Examples of Golang examples compared to Node.js for learning
This guide full of examples is intended for people learning Go that are coming from Node.js, although the vice versa can work too. This is not meant to be a complete guide and it is assumed that you've gone through the Tour of Go tutorial. This guide is meant to be barely good enough to help you at a high level understand how to do X in Y and doing further learning on your own is of course required.
- Examples
- comments
- printing
- logging
- variables
- types
- type check
- interpolation
- if/else
- for
- while
- switch
- arrays
- uint8 arrays
- array iteration
- buffers
- maps
- objects
- functions
- default values
- destructuring
- spread operator
- rest operator
- swapping
- classes
- generators
- datetime
- timeout
- interval
- IIFE
- files
- json
- big numbers
- promises
- async/await
- streams
- event emitter
- Contributing
- License
All sample code is available in examples/
// this is a line comment
/*
this is a block comment
*/package main
func main() {
// this is a line comment
/*
this is a block comment
*/
}console.log('print to stdout')
console.log('format %s %d', 'example', 1)
console.error('print to stderr')Output
print to stdout
format example 1
print to stderrpackage main
import (
"fmt"
"os"
)
func main() {
fmt.Println("print to stdout")
fmt.Printf("format %s %v\n", "example", 1)
fmt.Fprintf(os.Stderr, "print to stderr")
}Output
print to stdout
format example 1
print to stderrconsole.log((new Date()).toISOString(), 'hello world')Output
2021-04-11T20:55:07.451Z hello worldpackage main
import "log"
func main() {
log.Println("hello world")
}Output
2021/04/11 13:55:07 hello world(Package log writes to standard error ánd prints the date and time of each logged message)
// function scoped
var foo = 'foo'
// block scoped
let bar = 'bar'
// constant
const qux = 'qux'(variables are block scoped in Go)
package main
func main() {
// explicit
var foo string = "foo"
// type inferred
var bar = "foo"
// shorthand
baz := "bar"
// constant
const qux = "qux"
}const name = 'bob'
const age = 21
const message = `${name} is ${age} years old`
console.log(message)Output
bob is 21 years oldpackage main
import "fmt"
func main() {
name := "bob"
age := 21
message := fmt.Sprintf("%s is %d years old", name, age)
fmt.Println(message)
}Output
bob is 21 years old// primitives
const myBool = true
const myNumber = 10
const myString = 'foo'
const mySymbol = Symbol('bar')
const myNull = null
const myUndefined = undefined
// object types
const myObject = {}
const myArray = []
const myFunction = function() {}
const myError = new Error('error')
const myDate = new Date()
const myRegex = /a/
const myMap = new Map()
const mySet = new Set()
const myPromise = Promise.resolve()
const myGenerator = function *() {}
const myClass = class {}package main
func main() {
// primitives
var myBool bool = true
var myInt int = 10
var myInt8 int8 = 10
var myInt16 int16 = 10
var myInt32 int32 = 10
var myInt64 int64 = 10
var myUint uint = 10
var myUint8 uint8 = 10
var myUint16 uint16 = 10
var myUint32 uint32 = 10
var myUint64 uint64 = 10
var myUintptr uintptr = 10
var myFloat32 float32 = 10.5
var myFloat64 float64 = 10.5
var myComplex64 complex64 = -1 + 10i
var myComplex128 complex128 = -1 + 10i
var myString string = "foo"
var myByte byte = 10 // alias to uint8
var myRune rune = 'a' // alias to int32
// composite types
var myStruct struct{} = struct{}{}
var myArray []string = []string{}
var myMap map[string]int = map[string]int{}
var myFunction func() = func() {}
var myChannel chan bool = make(chan bool)
var myInterface interface{} = nil
var myPointer *int = new(int)
}function typeOf(obj) {
return {}.toString.call(obj).split(' ')[1].slice(0,-1).toLowerCase()
}
const values = [
true,
10,
'foo',
Symbol('bar'),
null,
undefined,
NaN,
{},
[],
function(){},
new Error(),
new Date(),
/a/,
new Map(),
new Set(),
Promise.resolve(),
function *() {},
class {},
]
for (value of values) {
console.log(typeOf(value))
}Output
boolean
number
string
symbol
null
undefined
number
object
array
function
error
date
regexp
map
set
promise
generatorfunction
functionpackage main
import (
"fmt"
"reflect"
"regexp"
"time"
)
func main() {
values := []interface{}{
true,
int8(10),
int16(10),
int32(10),
int64(10),
uint(10),
uint8(10),
uint16(10),
uint32(10),
uint64(10),
uintptr(10),
float32(10.5),
float64(10.5),
complex64(-1 + 10i),
complex128(-1 + 10i),
"foo",
byte(10),
'a',
rune('a'),
struct{}{},
[]string{},
map[string]int{},
func() {},
make(chan bool),
nil,
new(int),
time.Now(),
regexp.MustCompile(`^a$`),
}
for _, value := range values {
fmt.Println(reflect.TypeOf(value))
}
}Output
bool
int8
int16
int32
int64
uint
uint8
uint16
uint32
uint64
uintptr
float32
float64
complex64
complex128
string
uint8
int32
int32
struct {}
[]string
map[string]int
func()
chan bool
<nil>
*int
time.Time
*regexp.Regexpconst array = [1, 2]
if (array) {
console.log('array exists')
}
if (array.length === 2) {
console.log('length is 2')
} else if (array.length === 1) {
console.log('length is 1')
} else {
console.log('length is other')
}
const isOddLength = array.length % 2 == 1 ? 'yes' : 'no'
console.log(isOddLength)Output
array exists
length is 2
nopackage main
import "fmt"
func main() {
array := []byte{1, 2}
if array != nil {
fmt.Println("array exists")
}
if len(array) == 2 {
fmt.Println("length is 2")
} else if len(array) == 1 {
fmt.Println("length is 1")
} else {
fmt.Println("length is other")
}
// closest thing to ternary operator
isOddLength := "no"
if len(array)%2 == 1 {
isOddLength = "yes"
}
fmt.Println(isOddLength)
}Output
array exists
length is 2
nofor (let i = 0; i <= 5; i++) {
console.log(i)
}Output
0
1
2
3
4
5package main
import "fmt"
func main() {
for i := 0; i <= 5; i++ {
fmt.Println(i)
}
}Output
0
1
2
3
4
5let i = 0
while (i <= 5) {
console.log(i)
i++
}Output
0
1
2
3
4
5(there's no while keyword in Go but the same functionality is achieved by using for)
package main
import "fmt"
func main() {
i := 0
for i <= 5 {
fmt.Println(i)
i++
}
}Output
0
1
2
3
4
5const value = 'b'
switch(value) {
case 'a':
console.log('A')
break
case 'b':
console.log('B')
break
case 'c':
console.log('C')
break
default:
console.log('first default')
}
switch(value) {
case 'a':
console.log('A - falling through')
case 'b':
console.log('B - falling through')
case 'c':
console.log('C - falling through')
default:
console.log('second default')
}Output
B
B - falling through
C - falling through
second defaultpackage main
import "fmt"
func main() {
value := "b"
switch value {
case "a":
fmt.Println("A")
case "b":
fmt.Println("B")
case "c":
fmt.Println("C")
default:
fmt.Println("first default")
}
switch value {
case "a":
fmt.Println("A - falling through")
fallthrough
case "b":
fmt.Println("B - falling through")
fallthrough
case "c":
fmt.Println("C - falling through")
fallthrough
default:
fmt.Println("second default")
}
}Output
B
B - falling through
C - falling through
second defaultExamples of slicing, copying, appending, and prepending arrays.
const array = [1, 2, 3, 4, 5]
console.log(array)
const clone = array.slice(0)
console.log(clone)
const sub = array.slice(2,4)
console.log(sub)
const concatenated = clone.concat([6, 7])
console.log(concatenated)
const prepended = [-2,-1,0].concat(concatenated)
console.log(prepended)Output
[ 1, 2, 3, 4, 5 ]
[ 1, 2, 3, 4, 5 ]
[ 3, 4 ]
[ 1, 2, 3, 4, 5, 6, 7 ]
[ -2, -1, 0, 1, 2, 3, 4, 5, 6, 7 ]package main
import "fmt"
func main() {
array := []int{1, 2, 3, 4, 5}
fmt.Println(array)
clone := make([]int, len(array))
copy(clone, array)
fmt.Println(clone)
sub := array[2:4]
fmt.Println(sub)
concatenated := append(array, []int{6, 7}...)
fmt.Println(concatenated)
prepended := append([]int{-2, -1, 0}, concatenated...)
fmt.Println(prepended)
}Output
[1 2 3 4 5]
[1 2 3 4 5]
[3 4]
[1 2 3 4 5 6 7]
[-2 -1 0 1 2 3 4 5 6 7]const array = new Uint8Array(10)
console.log(array)
const offset = 1
array.set([1, 2, 3], offset)
console.log(array)
const sub = array.subarray(2)
console.log(sub)
const sub2 = array.subarray(2,4)
console.log(sub2)
console.log(array)
const value = 9
const start = 5
const end = 10
array.fill(value, start, end)
console.log(array)
console.log(array.byteLength)Output
Uint8Array [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ]
Uint8Array [ 0, 1, 2, 3, 0, 0, 0, 0, 0, 0 ]
Uint8Array [ 2, 3, 0, 0, 0, 0, 0, 0 ]
Uint8Array [ 2, 3 ]
Uint8Array [ 0, 1, 2, 3, 0, 0, 0, 0, 0, 0 ]
Uint8Array [ 0, 1, 2, 3, 0, 9, 9, 9, 9, 9 ]
10package main
import "fmt"
func main() {
array := make([]uint8, 10)
fmt.Println(array)
offset := 1
copy(array[offset:], []uint8{1, 2, 3})
fmt.Println(array)
sub := array[2:]
fmt.Println(sub)
sub2 := array[2:4]
fmt.Println(sub2)
fmt.Println(array)
value := uint8(9)
start := 5
end := 10
for i := start; i < end; i++ {
array[i] = value
}
fmt.Println(array)
fmt.Println(len(array))
}Output
[0 0 0 0 0 0 0 0 0 0]
[0 1 2 3 0 0 0 0 0 0]
[2 3 0 0 0 0 0 0]
[2 3]
[0 1 2 3 0 0 0 0 0 0]
[0 1 2 3 0 9 9 9 9 9]
10Examples of iterating, mapping, filtering, and reducing arrays.
const array = ['a', 'b', 'c']
array.forEach((value, i) => {
console.log(i, value)
})
const mapped = array.map(value => {
return value.toUpperCase()
})
console.log(mapped)
const filtered = array.filter((value, i) => {
return i % 2 == 0
})
console.log(filtered)
const reduced = array.reduce((acc, value, i) => {
if (i % 2 == 0) {
acc.push(value.toUpperCase())
}
return acc
}, [])
console.log(reduced)Output
0 'a'
1 'b'
2 'c'
[ 'A', 'B', 'C' ]
[ 'a', 'c' ]
[ 'A', 'C' ]package main
import (
"fmt"
"strings"
)
func main() {
array := []string{"a", "b", "c"}
for i, value := range array {
fmt.Println(i, value)
}
mapped := make([]string, len(array))
for i, value := range array {
mapped[i] = strings.ToUpper(value)
}
fmt.Println(mapped)
var filtered []string
for i, value := range array {
if i%2 == 0 {
filtered = append(filtered, value)
}
}
fmt.Println(filtered)
var reduced []string
for i, value := range array {
if i%2 == 0 {
reduced = append(reduced, strings.ToUpper(value))
}
}
fmt.Println(reduced)
}Output
0 a
1 b
2 c
[A B C]
[a c]
[A C]Examples of how to sort an array
const stringArray = ['a', 'd', 'z', 'b', 'c', 'y']
const stringArraySortedAsc = stringArray.sort((a, b) => a > b ? 1 : -1)
console.log(stringArraySortedAsc)
const stringArraySortedDesc = stringArray.sort((a, b) => a > b ? -1 : 1)
console.log(stringArraySortedDesc)
const numberArray = [1, 3, 5, 9, 4, 2, 0]
const numberArraySortedAsc = numberArray.sort((a, b) => a - b)
console.log(numberArraySortedAsc)
const numberArraySortedDesc = numberArray.sort((a, b) => b - a)
console.log(numberArraySortedDesc)
const collection = [
{
name: "Li L",
age: 8
},
{
name: "Json C",
age: 3
},
{
name: "Zack W",
age: 15
},
{
name: "Yi M",
age: 2
}
]
const collectionSortedByAgeAsc = collection.sort((a, b) => a.age - b.age)
console.log(collectionSortedByAgeAsc)
const collectionSortedByAgeDesc = collection.sort((a, b) => b.age - a.age)
console.log(collectionSortedByAgeDesc)Output
[ 'a', 'b', 'c', 'd', 'y', 'z' ]
[ 'z', 'y', 'd', 'c', 'b', 'a' ]
[ 0, 1, 2, 3, 4, 5, 9 ]
[ 9, 5, 4, 3, 2, 1, 0 ]
[ { name: 'Yi M', age: 2 },
{ name: 'Json C', age: 3 },
{ name: 'Li L', age: 8 },
{ name: 'Zack W', age: 15 } ]
[ { name: 'Zack W', age: 15 },
{ name: 'Li L', age: 8 },
{ name: 'Json C', age: 3 },
{ name: 'Yi M', age: 2 } ]package main
import (
"fmt"
"sort"
)
type Person struct {
Name string
Age int
}
type PersonCollection []Person
func (pc PersonCollection) Len() int {
return len(pc)
}
func (pc PersonCollection) Swap(i, j int) {
pc[i], pc[j] = pc[j], pc[i]
}
func (pc PersonCollection) Less(i, j int) bool {
// asc
return pc[i].Age < pc[j].Age
}
func main() {
intList := []int{1, 3, 5, 9, 4, 2, 0}
// asc
sort.Ints(intList)
fmt.Println(intList)
// desc
sort.Sort(sort.Reverse(sort.IntSlice(intList)))
fmt.Println(intList)
stringList := []string{"a", "d", "z", "b", "c", "y"}
// asc
sort.Strings(stringList)
fmt.Println(stringList)
// desc
sort.Sort(sort.Reverse(sort.StringSlice(stringList)))
fmt.Println(stringList)
collection := []Person{
{"Li L", 8},
{"Json C", 3},
{"Zack W", 15},
{"Yi M", 2},
}
// asc
sort.Sort(PersonCollection(collection))
fmt.Println(collection)
// desc
sort.Sort(sort.Reverse(PersonCollection(collection)))
fmt.Println(collection)
}Output
[0 1 2 3 4 5 9]
[9 5 4 3 2 1 0]
[a b c d y z]
[z y d c b a]
[{Yi M 2} {Json C 3} {Li L 8} {Zack W 15}]
[{Zack W 15} {Li L 8} {Json C 3} {Yi M 2}]Examples of how to allocate a buffer, write in big or little endian format, encode to a hex string, and check if buffers are equal.
const buf = Buffer.alloc(6)
let value = 0x1234567890ab
let offset = 0
let byteLength = 6
buf.writeUIntBE(value, offset, byteLength)
let hexstr = buf.toString('hex')
console.log(hexstr)
const buf2 = Buffer.alloc(6)
value = 0x1234567890ab
offset = 0
byteLength = 6
buf2.writeUIntLE(value, offset, byteLength)
hexstr = buf2.toString('hex')
console.log(hexstr)
let isEqual = Buffer.compare(buf, buf2) === 0
console.log(isEqual)
isEqual = Buffer.compare(buf, buf) === 0
console.log(isEqual)Output
1234567890ab
ab9078563412
false
truepackage main
import (
"bytes"
"encoding/binary"
"encoding/hex"
"fmt"
"log"
"math/big"
"reflect"
)
func writeUIntBE(buffer []byte, value, offset, byteLength int64) {
slice := make([]byte, byteLength)
val := new(big.Int)
val.SetUint64(uint64(value))
valBytes := val.Bytes()
buf := bytes.NewBuffer(slice)
err := binary.Write(buf, binary.BigEndian, &valBytes)
if err != nil {
log.Fatal(err)
}
slice = buf.Bytes()
slice = slice[int64(len(slice))-byteLength : len(slice)]
copy(buffer[offset:], slice)
}
func writeUIntLE(buffer []byte, value, offset, byteLength int64) {
slice := make([]byte, byteLength)
val := new(big.Int)
val.SetUint64(uint64(value))
valBytes := val.Bytes()
tmp := make([]byte, len(valBytes))
for i := range valBytes {
tmp[i] = valBytes[len(valBytes)-1-i]
}
copy(slice, tmp)
copy(buffer[offset:], slice)
}
func main() {
buf := make([]byte, 6)
writeUIntBE(buf, 0x1234567890ab, 0, 6)
fmt.Println(hex.EncodeToString(buf))
buf2 := make([]byte, 6)
writeUIntLE(buf2, 0x1234567890ab, 0, 6)
fmt.Println(hex.EncodeToString(buf2))
isEqual := reflect.DeepEqual(buf, buf2)
fmt.Println(isEqual)
isEqual = reflect.DeepEqual(buf, buf)
fmt.Println(isEqual)
}Output
1234567890ab
ab9078563412
false
trueconst map = new Map()
map.set('foo', 'bar')
let found = map.has('foo')
console.log(found)
let item = map.get('foo')
console.log(item)
map.delete('foo')
found = map.has('foo')
console.log(found)
item = map.get('foo')
console.log(item)
const map2 = {}
map2['foo'] = 'bar'
item = map2['foo']
delete map2['foo']
const map3 = new Map()
map3.set('foo', 100)
map3.set('bar', 200)
map3.set('baz', 300)
for (let [key, value] of map3) {
console.log(key, value)
}Output
true
bar
false
undefined
foo 100
bar 200
baz 300package main
import "fmt"
func main() {
map1 := make(map[string]string)
map1["foo"] = "bar"
item, found := map1["foo"]
fmt.Println(found)
fmt.Println(item)
delete(map1, "foo")
item, found = map1["foo"]
fmt.Println(found)
fmt.Println(item)
map2 := make(map[string]int)
map2["foo"] = 100
map2["bar"] = 200
map2["baz"] = 300
for key, value := range map2 {
fmt.Println(key, value)
}
}Output
true
bar
false
foo 100
bar 200
baz 300const obj = {
someProperties: {
'foo': 'bar'
},
someMethod: (prop) => {
return obj.someProperties[prop]
}
}
let item = obj.someProperties['foo']
console.log(item)
item = obj.someMethod('foo')
console.log(item)Output
bar
barpackage main
import "fmt"
type Obj struct {
SomeProperties map[string]string
}
func NewObj() *Obj {
return &Obj{
SomeProperties: map[string]string{
"foo": "bar",
},
}
}
func (o *Obj) SomeMethod(prop string) string {
return o.SomeProperties[prop]
}
func main() {
obj := NewObj()
item := obj.SomeProperties["foo"]
fmt.Println(item)
item = obj.SomeMethod("foo")
fmt.Println(item)
}Output
bar
barfunction add(a, b) {
return a + b
}
const result = add(2,3)
console.log(result)Output
5package main
import "fmt"
func add(a int, b int) int {
return a + b
}
func main() {
result := add(2, 3)
fmt.Println(result)
}Output
5function greet(name = 'stranger') {
return `hello ${name}`
}
let message = greet()
console.log(message)
message = greet('bob')
console.log(message)Output
hello stranger
hello bobuse pointers and check for nil to know if explicitly left blank
package main
import "fmt"
func greet(name *string) string {
n := "stranger"
if name != nil {
n = *name
}
return fmt.Sprintf("hello %s", n)
}
func main() {
message := greet(nil)
fmt.Println(message)
name := "bob"
message = greet(&name)
fmt.Println(message)
}Output
hello stranger
hello bobconst obj = { key: 'foo', value: 'bar' }
const { key, value } = obj
console.log(key, value)Output
foo barpackage main
import "fmt"
type Obj struct {
Key string
Value string
}
func (o *Obj) Read() (string, string) {
return o.Key, o.Value
}
func main() {
obj := Obj{
Key: "foo",
Value: "bar",
}
// option 1: multiple variable assignment
key, value := obj.Key, obj.Value
fmt.Println(key, value)
// option 2: return multiple values from a function
key, value = obj.Read()
fmt.Println(key, value)
}Output
foo bar
foo barconst array = [1, 2, 3, 4, 5]
console.log(...array)Output
1 2 3 4 5package main
import "fmt"
func main() {
array := []byte{1, 2, 3, 4, 5}
var i []interface{}
for _, value := range array {
i = append(i, value)
}
fmt.Println(i...)
}Output
1 2 3 4 5function sum(...nums) {
let t = 0
for (let n of nums) {
t += n
}
return t
}
const total = sum(1, 2, 3, 4, 5)
console.log(total)Output
15package main
import "fmt"
func sum(nums ...int) int {
var t int
for _, n := range nums {
t += n
}
return t
}
func main() {
total := sum(1, 2, 3, 4, 5)
fmt.Println(total)
}Output
15let a = 'foo'
let b = 'bar'
console.log(a, b);
[b, a] = [a, b]
console.log(a, b)Output
foo bar
bar foopackage main
import "fmt"
func main() {
a := "foo"
b := "bar"
fmt.Println(a, b)
b, a = a, b
fmt.Println(a, b)
}Output
foo bar
bar fooExamples of classes, constructors, instantiation, and "this" keyword.
class Foo {
constructor(value) {
this.item = value
}
getItem() {
return this.item
}
setItem(value) {
this.item = value
}
}
const foo = new Foo('bar')
console.log(foo.item)
foo.setItem('qux')
const item = foo.getItem()
console.log(item)Output
bar
qux(closest thing to a class is to use a structure)
package main
import "fmt"
type Foo struct {
Item string
}
func NewFoo(value string) *Foo {
return &Foo{
Item: value,
}
}
func (f *Foo) GetItem() string {
return f.Item
}
func (f *Foo) SetItem(value string) {
f.Item = value
}
func main() {
foo := NewFoo("bar")
fmt.Println(foo.Item)
foo.SetItem("qux")
item := foo.GetItem()
fmt.Println(item)
}Output
bar
quxfunction *generator() {
yield 'hello'
yield 'world'
}
let gen = generator()
while (true) {
let { value, done } = gen.next()
console.log(value, done)
if (done) {
break
}
}
// alternatively
for (let value of generator()) {
console.log(value)
}Output
hello false
world false
undefined true
hello
worldpackage main
import "fmt"
func Generator() chan string {
c := make(chan string)
go func() {
c <- "hello"
c <- "world"
close(c)
}()
return c
}
func GeneratorFunc() func() (string, bool) {
s := []string{"hello", "world"}
i := -1
return func() (string, bool) {
i++
if i >= len(s) {
return "", false
}
return s[i], true
}
}
func main() {
gen := Generator()
for {
value, more := <-gen
fmt.Println(value, more)
if !more {
break
}
}
// alternatively
for value := range Generator() {
fmt.Println(value)
}
// alternatively
genfn := GeneratorFunc()
for {
value, more := genfn()
fmt.Println(value, more)
if !more {
break
}
}
}Output
hello true
world true
false
hello
world
hello true
world true
falseExamples of parsing, formatting, and getting unix timestamp of dates.
const nowUnix = Date.now()
console.log(nowUnix)
const datestr = '2019-01-17T09:24:23+00:00'
const date = new Date(datestr)
console.log(date.getTime())
console.log(date.toString())
const futureDate = new Date(date)
futureDate.setDate(date.getDate()+14)
console.log(futureDate.toString())
const formatted = `${String(date.getMonth()+1).padStart(2, 0)}/${String(date.getDate()).padStart(2, 0)}/${date.getFullYear()}`
console.log(formatted)Output
1547718844168
1547717063000
Thu Jan 17 2019 01:24:23 GMT-0800 (Pacific Standard Time)
Thu Jan 31 2019 01:24:23 GMT-0800 (Pacific Standard Time)
01/17/2019package main
import (
"fmt"
"time"
)
func main() {
nowUnix := time.Now().Unix()
fmt.Println(nowUnix)
datestr := "2019-01-17T09:24:23+00:00"
date, err := time.Parse("2006-01-02T15:04:05Z07:00", datestr)
if err != nil {
panic(err)
}
fmt.Println(date.Unix())
fmt.Println(date.String())
futureDate := date.AddDate(0, 0, 14)
fmt.Println(futureDate.String())
formatted := date.Format("01/02/2006")
fmt.Println(formatted)
}Output
1547718844
1547717063
2019-01-17 09:24:23 +0000 +0000
2019-01-31 09:24:23 +0000 +0000
01/17/2019setTimeout(callback, 1e3)
function callback() {
console.log('called')
}Output
calledpackage main
import (
"fmt"
"sync"
"time"
)
var wg sync.WaitGroup
func callback() {
defer wg.Done()
fmt.Println("called")
}
func main() {
wg.Add(1)
time.AfterFunc(1*time.Second, callback)
wg.Wait()
}Output
calledlet i = 0
const id = setInterval(callback, 1e3)
function callback() {
console.log('called', i)
if (i === 3) {
clearInterval(id)
}
i++
}Output
called 0
called 1
called 2
called 3package main
import (
"fmt"
"time"
)
func callback(i int) {
fmt.Println("called", i)
}
func main() {
ticker := time.NewTicker(1 * time.Second)
i := 0
for range ticker.C {
callback(i)
if i == 3 {
ticker.Stop()
break
}
i++
}
}Output
called 0
called 1
called 2
called 3Immediately invoked function expression
(function(name) {
console.log('hello', name)
})('bob')Output
hello bobpackage main
import "fmt"
func main() {
func(name string) {
fmt.Println("hello", name)
}("bob")
}Output
hello bobExamples of creating, opening, writing, reading, closing, and deleting files.
const fs = require('fs')
// create file
fs.closeSync(fs.openSync('test.txt', 'w'))
// open file (returns file descriptor)
const fd = fs.openSync('test.txt', 'r+')
let wbuf = Buffer.from('hello world.')
let rbuf = Buffer.alloc(12)
let off = 0
let len = 12
let pos = 0
// write file
fs.writeSync(fd, wbuf, pos)
// read file
fs.readSync(fd, rbuf, off, len, pos)
console.log(rbuf.toString())
// close file
fs.closeSync(fd)
// delete file
fs.unlinkSync('test.txt')Output
hello world.package main
import (
"fmt"
"os"
"syscall"
)
func main() {
// create file
file, err := os.Create("test.txt")
if err != nil {
panic(err)
}
// close file
file.Close()
// open file
file, err = os.OpenFile("test.txt", os.O_RDWR, 0755)
if err != nil {
panic(err)
}
// file descriptor
fd := file.Fd()
// open file (using file descriptor)
file = os.NewFile(fd, "test file")
wbuf := []byte("hello world.")
rbuf := make([]byte, 12)
var off int64
// write file
if _, err := file.WriteAt(wbuf, off); err != nil {
panic(err)
}
// read file
if _, err := file.ReadAt(rbuf, off); err != nil {
panic(err)
}
fmt.Println(string(rbuf))
// close file (using file descriptor)
if err := syscall.Close(int(fd)); err != nil {
panic(err)
}
// delete file
if err := os.Remove("test.txt"); err != nil {
panic(err)
}
}Output
hello world.Examples of how to parse (unmarshal) and stringify (marshal) JSON.
let jsonstr = '{"foo":"bar"}'
let parsed = JSON.parse(jsonstr)
console.log(parsed)
jsonstr = JSON.stringify(parsed)
console.log(jsonstr)Output
{ foo: 'bar' }
{"foo":"bar"}package main
import (
"encoding/json"
"fmt"
)
type T struct {
Foo string `json:"foo"`
}
func main() {
jsonstr := `{"foo":"bar"}`
t := new(T)
err := json.Unmarshal([]byte(jsonstr), t)
if err != nil {
panic(err)
}
fmt.Println(t)
marshalled, err := json.Marshal(t)
jsonstr = string(marshalled)
fmt.Println(jsonstr)
}Output
&{bar}
{"foo":"bar"}Examples of creating big number types from and to uint, string, hex, and buffers.
let bn = 75n;
console.log(bn.toString(10))
bn = BigInt('75')
console.log(bn.toString(10))
bn = BigInt(0x4b)
console.log(bn.toString(10))
bn = BigInt('0x4b')
console.log(bn.toString(10))
bn = BigInt('0x' + Buffer.from('4b', 'hex').toString('hex'))
console.log(bn.toString(10))
console.log(Number(bn))
console.log(bn.toString(16))
console.log(Buffer.from(bn.toString(16), 'hex'))
let bn2 = BigInt(100)
let isEqual = bn === bn2
console.log(isEqual)
let isGreater = bn > bn2
console.log(isGreater)
let isLesser = bn < bn2
console.log(isLesser)Output
75
75
75
75
75
75
4b
<Buffer 4b>
false
false
truepackage main
import (
"encoding/hex"
"fmt"
"math/big"
)
func main() {
bn := new(big.Int)
bn.SetUint64(75)
fmt.Println(bn.String())
bn = new(big.Int)
bn.SetString("75", 10)
fmt.Println(bn.String())
bn = new(big.Int)
bn.SetUint64(0x4b)
fmt.Println(bn.String())
bn = new(big.Int)
bn.SetString("4b", 16)
fmt.Println(bn.String())
bn = new(big.Int)
bn.SetBytes([]byte{0x4b})
fmt.Println(bn.String())
fmt.Println(bn.Uint64())
fmt.Println(hex.EncodeToString(bn.Bytes()))
fmt.Println(bn.Bytes())
bn2 := big.NewInt(100)
isEqual := bn.Cmp(bn2) == 0
fmt.Println(isEqual)
isGreater := bn.Cmp(bn2) == 1
fmt.Println(isGreater)
isLesser := bn.Cmp(bn2) == -1
fmt.Println(isLesser)
}Output
75
75
75
75
75
75
4b
[75]
false
false
truefunction asyncMethod(value) {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve('resolved: ' + value)
}, 1e3)
})
}
function main() {
asyncMethod('foo')
.then(result => console.log(result))
.catch(err => console.error(err))
Promise.all([
asyncMethod('A'),
asyncMethod('B'),
asyncMethod('C')
])
.then(result => console.log(result))
.catch(err => console.error(err))
}
main()Output
resolved: foo
[ 'resolved: A', 'resolved: B', 'resolved: C' ](closest thing is to use channels)
package main
import (
"fmt"
"sync"
"time"
"github.com/prometheus/common/log"
)
func asyncMethod(value string) chan interface{} {
ch := make(chan interface{}, 1)
go func() {
time.Sleep(1 * time.Second)
ch <- "resolved: " + value
close(ch)
}()
return ch
}
func resolveAll(ch ...chan interface{}) chan interface{} {
var wg sync.WaitGroup
res := make([]string, len(ch))
resCh := make(chan interface{}, 1)
go func() {
for i, c := range ch {
wg.Add(1)
go func(j int, ifcCh chan interface{}) {
ifc := <-ifcCh
switch v := ifc.(type) {
case error:
resCh <- v
case string:
res[j] = v
}
wg.Done()
}(i, c)
}
wg.Wait()
resCh <- res
close(resCh)
}()
return resCh
}
func main() {
var wg sync.WaitGroup
wg.Add(2)
go func() {
result := <-asyncMethod("foo")
switch v := result.(type) {
case string:
fmt.Println(v)
case error:
log.Errorln(v)
}
wg.Done()
}()
go func() {
result := <-resolveAll(
asyncMethod("A"),
asyncMethod("B"),
asyncMethod("C"),
)
switch v := result.(type) {
case []string:
fmt.Println(v)
case error:
log.Errorln(v)
}
wg.Done()
}()
wg.Wait()
}Output
resolved: foo
[resolved: A resolved: B resolved: C]function hello(name) {
return new Promise((resolve, reject) => {
setTimeout(() => {
if (name === 'fail') {
reject(new Error('failed'))
} else {
resolve('hello ' + name)
}
}, 1e3)
})
}
async function main() {
try {
let output = await hello('bob')
console.log(output)
output = await hello('fail')
console.log(output)
} catch(err) {
console.log(err.message)
}
}
main()Output
hello bob
failed(closest thing is to use channels)
package main
import (
"errors"
"fmt"
"time"
"github.com/prometheus/common/log"
)
func hello(name string) chan interface{} {
ch := make(chan interface{}, 1)
go func() {
time.Sleep(1 * time.Second)
if name == "fail" {
ch <- errors.New("failed")
} else {
ch <- "hello " + name
}
}()
return ch
}
func main() {
result := <-hello("bob")
switch v := result.(type) {
case string:
fmt.Println(v)
case error:
log.Errorln(v)
}
result = <-hello("fail")
switch v := result.(type) {
case string:
fmt.Println(v)
case error:
log.Errorln(v)
}
}Output
hello bob
failedExamples of reading and writing streams
const { Readable, Writable } = require('stream')
const inStream = new Readable()
inStream.push(Buffer.from('foo'))
inStream.push(Buffer.from('bar'))
inStream.push(null) // end stream
inStream.pipe(process.stdout)
const outStream = new Writable({
write(chunk, encoding, callback) {
console.log('received: ' + chunk.toString('utf8'))
callback()
}
})
outStream.write(Buffer.from('abc'))
outStream.write(Buffer.from('xyz'))
outStream.end()Output
foobar
received: abc
received: xyzpackage main
import (
"bufio"
"bytes"
"fmt"
"io"
"os"
"runtime"
)
func main() {
inStream := new(bytes.Buffer)
w := bufio.NewWriter(inStream)
_, err := w.Write([]byte("foo"))
if err != nil {
panic(err)
}
_, err = w.Write([]byte("bar"))
if err != nil {
panic(err)
}
err = w.Flush()
if err != nil {
panic(err)
}
inStream.WriteTo(os.Stdout)
fmt.Print("\n")
outStream := new(bytes.Buffer)
outStream.Write([]byte("abc\n"))
outStream.Write([]byte("xyc\n"))
piper, pipew := io.Pipe()
go func() {
sc := bufio.NewScanner(piper)
for sc.Scan() {
fmt.Println("received: " + sc.Text())
}
if err := sc.Err(); err != nil {
panic(err)
}
os.Exit(0)
}()
go func() {
defer pipew.Close()
io.Copy(pipew, outStream)
}()
defer runtime.Goexit()
}Output
foobar
received: abc
received: xycconst EventEmitter = require('events')
class MyEmitter extends EventEmitter {}
const myEmitter = new MyEmitter()
myEmitter.on('my-event', msg => {
console.log(msg)
})
myEmitter.on('my-other-event', msg => {
console.log(msg)
})
myEmitter.emit('my-event', 'hello world')
myEmitter.emit('my-other-event', 'hello other world')Output
hello world
hello other world(closest thing is to use channels)
package main
import (
"fmt"
)
type MyEmitter map[string]chan string
func main() {
myEmitter := MyEmitter{}
myEmitter["my-event"] = make(chan string)
myEmitter["my-other-event"] = make(chan string)
go func() {
for {
select {
case msg := <-myEmitter["my-event"]:
fmt.Println(msg)
case msg := <-myEmitter["my-other-event"]:
fmt.Println(msg)
}
}
}()
myEmitter["my-event"] <- "hello world"
myEmitter["my-other-event"] <- "hello other world"
}Output
hello world
hello other worldconst err1 = new Error('some error')
console.log(err1)
class FooError extends Error{
constructor(message) {
super(message)
this.name = 'FooError'
this.message = message
}
toString() {
return this.message
}
}
const err2 = new FooError('my custom error')
console.log(err2)Output
Error: some error
{ FooError: my custom error }package main
import (
"errors"
"fmt"
)
type FooError struct {
s string
}
func (f *FooError) Error() string {
return f.s
}
func NewFooError(s string) error {
return &FooError{s}
}
func main() {
err1 := errors.New("some error")
fmt.Println(err1)
err2 := NewFooError("my custom error")
fmt.Println(err2)
}Output
some error
my custom errorfunction foo(fail) {
if (fail) {
throw Error('my error')
}
}
function main() {
try {
foo(true)
} catch(err) {
console.log(`caught error: ${err.message}`)
}
}
main()Output
caught error: my errorpackage main
import (
"errors"
"fmt"
)
func foo(fail bool) error {
if fail {
return errors.New("my error")
}
return nil
}
func main() {
err := foo(true)
if err != nil {
fmt.Printf("caught error: %s\n", err.Error())
}
}Output
caught error: my errorfunction foo() {
throw Error('my exception')
}
function main() {
foo()
}
process.on('uncaughtException', err => {
console.log(`caught exception: ${err.message}`)
process.exit(1)
})
main()Output
caught exception: my exceptionpackage main
import (
"fmt"
)
func foo() {
panic("my exception")
}
func main() {
defer func() {
if r := recover(); r != nil {
fmt.Printf("caught exception: %s", r)
}
}()
foo()
}Output
caught exception: my exceptionlet input = 'foobar'
let replaced = input.replace(/foo(.*)/i, 'qux$1')
console.log(replaced)
let match = /o{2}/i.test(input)
console.log(match)
input = '111-222-333'
let matches = input.match(/([0-9]+)/gi)
console.log(matches)Output
quxbar
true
[ '111', '222', '333' ]package main
import (
"fmt"
"regexp"
)
func main() {
input := "foobar"
re := regexp.MustCompile(`(?i)foo(.*)`)
replaced := re.ReplaceAllString(input, "qux$1")
fmt.Println(replaced)
re = regexp.MustCompile(`(?i)o{2}`)
match := re.Match([]byte(input))
fmt.Println(match)
input = "111-222-333"
re = regexp.MustCompile(`(?i)([0-9]+)`)
matches := re.FindAllString(input, -1)
fmt.Println(matches)
}Output
quxbar
true
[111 222 333]const { execSync } = require('child_process')
const output = execSync(`echo 'hello world'`)
console.log(output.toString())Output
hello worldpackage main
import (
"fmt"
"os/exec"
)
func main() {
output, err := exec.Command("echo", "hello world").Output()
if err != nil {
panic(err)
}
fmt.Println(string(output))
}Output
hello worldconst { exec } = require('child_process')
exec(`echo 'hello world'`, (error, stdout, stderr) => {
if (error) {
console.error(err)
}
if (stderr) {
console.error(stderr)
}
if (stdout) {
console.log(stdout)
}
})Output
hello worldpackage main
import (
"os"
"os/exec"
)
func main() {
cmd := exec.Command("echo", "hello world")
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
cmd.Run()
}Output
hello worldconst net = require('net')
function handler(socket) {
socket.write('Received: ')
socket.pipe(socket)
}
const server = net.createServer(handler)
server.listen(3000)Output
$ echo 'hello' | nc localhost 3000
Received: hellopackage main
import (
"bufio"
"net"
)
func handler(conn net.Conn) {
defer conn.Close()
reader := bufio.NewReader(conn)
for {
message, err := reader.ReadString('\n')
if err != nil {
return
}
conn.Write([]byte("Received: "))
conn.Write([]byte(message))
}
}
func main() {
listener, err := net.Listen("tcp", ":3000")
if err != nil {
panic(err)
}
defer listener.Close()
for {
conn, err := listener.Accept()
if err != nil {
panic(err)
}
go handler(conn)
}
}Output
$ echo 'hello' | nc localhost 3000
Received: helloconst dgram = require('dgram')
const server = dgram.createSocket('udp4')
server.on('error', err => {
console.error(err)
server.close()
})
server.on('message', (msg, rinfo) => {
const data = msg.toString('utf8').trim()
console.log(`received: ${data} from ${rinfo.address}:${rinfo.port}`)
})
server.on('listening', () => {
const address = server.address()
console.log(`server listening ${address.address}:${address.port}`)
})
server.bind(3000)Output
$ echo 'hello world' > /dev/udp/0.0.0.0/3000
server listening 0.0.0.0:3000
received: hello world from 127.0.0.1:51452package main
import (
"fmt"
"net"
"strings"
)
func main() {
conn, err := net.ListenUDP("udp", &net.UDPAddr{
Port: 3000,
IP: net.ParseIP("0.0.0.0"),
})
if err != nil {
panic(err)
}
defer conn.Close()
fmt.Printf("server listening %s\n", conn.LocalAddr().String())
for {
message := make([]byte, 20)
rlen, remote, err := conn.ReadFromUDP(message[:])
if err != nil {
panic(err)
}
data := strings.TrimSpace(string(message[:rlen]))
fmt.Printf("received: %s from %s\n", data, remote)
}
}Output
$ echo 'hello world' > /dev/udp/0.0.0.0/3000
server listening [::]:3000
received: hello world from 127.0.0.1:50275const http = require('http')
function handler(request, response) {
response.writeHead(200, { 'Content-type':'text/plain' })
response.write('hello world')
response.end()
}
const server = http.createServer(handler)
server.listen(8080)Output
$ curl http://localhost:8080
hello worldpackage main
import (
"net/http"
)
func handler(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(200)
w.Write([]byte("hello world"))
}
func main() {
http.HandleFunc("/", handler)
if err := http.ListenAndServe(":8080", nil); err != nil {
panic(err)
}
}Output
$ curl http://localhost:8080
hello worldconst url = require('url')
const qs = require('querystring')
const urlstr = 'http://bob:secret@sub.example.com:8080/somepath?foo=bar'
const parsed = url.parse(urlstr)
console.log(parsed.protocol)
console.log(parsed.auth)
console.log(parsed.port)
console.log(parsed.hostname)
console.log(parsed.pathname)
console.log(qs.parse(parsed.search.substr(1)))Output
http:
bob:secret
8080
sub.example.com
/somepath
{ foo: 'bar' }package main
import (
"fmt"
"net/url"
)
func main() {
urlstr := "http://bob:secret@sub.example.com:8080/somepath?foo=bar"
u, err := url.Parse(urlstr)
if err != nil {
panic(err)
}
fmt.Println(u.Scheme)
fmt.Println(u.User)
fmt.Println(u.Port())
fmt.Println(u.Hostname())
fmt.Println(u.Path)
fmt.Println(u.Query())
}Output
http
bob:secret
8080
sub.example.com
/somepath
map[foo:[bar]]const zlib = require('zlib')
const data = Buffer.from('hello world', 'utf-8')
zlib.gzip(data, (err, compressed) => {
if (err) {
console.error(err)
}
console.log(compressed)
zlib.unzip(compressed, (err, decompressed) => {
if (err) {
console.error(err)
}
console.log(decompressed.toString())
})
})Output
<Buffer 1f 8b 08 00 00 00 00 00 00 13 cb 48 cd c9 c9 57 28 cf 2f ca 49 01 00 85 11 4a 0d 0b 00 00 00>
hello worldpackage main
import (
"bytes"
"compress/gzip"
"fmt"
)
func main() {
data := []byte("hello world")
compressed := new(bytes.Buffer)
w := gzip.NewWriter(compressed)
if _, err := w.Write(data); err != nil {
panic(err)
}
if err := w.Close(); err != nil {
panic(err)
}
fmt.Println(compressed.Bytes())
decompressed := new(bytes.Buffer)
r, err := gzip.NewReader(compressed)
if err != nil {
panic(err)
}
_, err = decompressed.ReadFrom(r)
if err != nil {
panic(err)
}
fmt.Println(string(decompressed.Bytes()))
}Output
[31 139 8 0 0 0 0 0 0 255 202 72 205 201 201 87 40 207 47 202 73 1 4 0 0 255 255 133 17 74 13 11 0 0 0]
hello worldDNS lookup examples
const dns = require('dns')
dns.resolveNs('google.com', (err, ns) => {
if (err) {
console.error(err)
}
console.log(ns)
})
dns.resolve4('google.com', (err, ips) => {
if (err) {
console.error(err)
}
console.log(ips)
})
dns.resolveMx('google.com', (err, mx) => {
if (err) {
console.error(err)
}
console.log(mx)
})
dns.resolveTxt('google.com', (err, txt) => {
if (err) {
console.error(err)
}
console.log(txt)
})
dns.setServers(['1.1.1.1'])
console.log(dns.getServers())
dns.resolveNs('google.com', (err, ns) => {
if (err) {
console.error(err)
}
console.log(ns)
})Output
[
'ns2.google.com',
'ns3.google.com',
'ns4.google.com',
'ns1.google.com'
]
[ '172.217.11.78' ]
[ { exchange: 'alt4.aspmx.l.google.com', priority: 50 },
{ exchange: 'alt2.aspmx.l.google.com', priority: 30 },
{ exchange: 'alt3.aspmx.l.google.com', priority: 40 },
{ exchange: 'aspmx.l.google.com', priority: 10 },
{ exchange: 'alt1.aspmx.l.google.com', priority: 20 } ]
[ [ 'v=spf1 include:_spf.google.com ~all' ],
[ 'docusign=05958488-4752-4ef2-95eb-aa7ba8a3bd0e' ],
[ 'facebook-domain-verification=22rm551cu4k0ab0bxsw536tlds4h95' ],
[ 'globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8=' ] ]
[ '1.1.1.1' ]
[
'ns1.google.com',
'ns2.google.com',
'ns4.google.com',
'ns3.google.com'
]package main
import (
"fmt"
"net"
)
func main() {
ns, err := net.LookupNS("google.com")
if err != nil {
panic(err)
}
fmt.Printf("%s\n", ns)
ips, err := net.LookupIP("google.com")
if err != nil {
panic(err)
}
fmt.Println(ips)
mx, err := net.LookupMX("google.com")
if err != nil {
panic(err)
}
fmt.Println(mx)
txt, err := net.LookupTXT("google.com")
if err != nil {
panic(err)
}
fmt.Println(txt)
r := &net.Resolver{
PreferGo: true,
Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
d := net.Dialer{
Timeout: time.Millisecond * time.Duration(10_000),
}
return d.DialContext(ctx, "udp", "1.1.1.1:53")
},
}
ns, _ = r.LookupNS(context.Background(), "google.com")
fmt.Printf("%s", ns)
}Output
[%!s(*net.NS=&{ns3.google.com.}) %!s(*net.NS=&{ns4.google.com.}) %!s(*net.NS=&{ns1.google.com.}) %!s(*net.NS=&{ns2.google.com.})]
[172.217.5.78 2607:f8b0:4007:80d::200e]
[0xc0000ba2e0 0xc0000ba260 0xc0000ba2a0 0xc0000ba280 0xc0000ba300]
[facebook-domain-verification=22rm551cu4k0ab0bxsw536tlds4h95 docusign=05958488-4752-4ef2-95eb-aa7ba8a3bd0e v=spf1 include:_spf.google.com ~all globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8=]
[%!s(*net.NS=&{ns2.google.com.}) %!s(*net.NS=&{ns1.google.com.}) %!s(*net.NS=&{ns3.google.com.}) %!s(*net.NS=&{ns4.google.com.})]const crypto = require('crypto')
const hash = crypto.createHash('sha256').update(Buffer.from('hello')).digest()
console.log(hash.toString('hex'))Output
2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824package main
import (
"crypto/sha256"
"encoding/hex"
"fmt"
)
func main() {
hash := sha256.Sum256([]byte("hello"))
fmt.Println(hex.EncodeToString(hash[:]))
}Output
2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824const key = process.env['API_KEY']
console.log(key)Output
$ API_KEY=foobar node examples/env_vars.js
foobarpackage main
import (
"fmt"
"os"
)
func main() {
key := os.Getenv("API_KEY")
fmt.Println(key)
}Output
$ API_KEY=foobar go run examples/env_vars.go
foobarconst args = process.argv.slice(2)
console.log(args)Output
$ node examples/cli_args.js foo bar qux
[ 'foo', 'bar', 'qux' ]package main
import (
"fmt"
"os"
)
func main() {
args := os.Args[1:]
fmt.Println(args)
}Output
$ go run examples/cli_args.go foo bar qux
[foo bar qux]const yargs = require('yargs')
const { foo='default value', qux=false } = yargs.argv
console.log('foo:', foo)
console.log('qux:', qux)Output
$ node examples/cli_flags.js --foo='bar' --qux=true
foo: bar
qux: truepackage main
import (
"flag"
"fmt"
)
func main() {
var foo string
flag.StringVar(&foo, "foo", "default value", "a string var")
var qux bool
flag.BoolVar(&qux, "qux", false, "a bool var")
flag.Parse()
fmt.Println("foo:", foo)
fmt.Println("qux:", qux)
}Output
$ go run examples/cli_flags.go -foo='bar' -qux=true
foo: bar
qux: trueprocess.stdout.write('hello world\n')Output
hello worldpackage main
import (
"fmt"
"os"
)
func main() {
fmt.Fprint(os.Stdout, "hello world\n")
}Output
hello worldprocess.stderr.write('hello error\n')Output
hello errorpackage main
import (
"fmt"
"os"
)
func main() {
fmt.Fprint(os.Stderr, "hello error\n")
}Output
hello errorconst stdin = process.openStdin()
process.stdout.write('Enter name: ')
stdin.addListener('data', text => {
const name = text.toString().trim()
console.log('Your name is: ' + name)
stdin.pause()
})Output
Enter name: bob
Your name is: bobpackage main
import (
"bufio"
"fmt"
"os"
"strings"
)
func main() {
reader := bufio.NewReader(os.Stdin)
fmt.Print("Enter name: ")
text, err := reader.ReadString('\n')
if err != nil {
panic(err)
}
name := strings.TrimSpace(text)
fmt.Printf("Your name is: %s\n", name)
}Output
Enter name: bob
Your name is: bob# initializing metadata and dependencies file (package.json)
$ npm init
# installing a module
$ npm install moment --save
# updating a module
$ npm install moment@latest --save
# removing a module
$ npm uninstall moment --save
# pruning modules (removing unused modules)
$ npm prune
# publishing a module
$ npm publish// importing a module
const moment = require('moment')
const now = moment().unix()
console.log(now)Output
1546595748// exporting a module
module.exports = {
greet(name) {
console.log(`hello ${name}`)
}
}// importing exported module
const greeter = require('./greeter')
greeter.greet('bob')Output
hello bobSetup
# enable Go modules support
GO111MODULE=on
# initializing dependencies file (go.mod)
$ go mod init
# installing a module
$ go get github.com/go-shadow/moment
# updating a module
$ go get -u github.com/go-shadow/moment
# removing a module
$ rm -rf $GOPATH/pkg/mod/github.com/go-shadow/moment@v<tag>-<checksum>/
# pruning modules (removing unused modules from dependencies file)
$ go mod tidy
# download modules being used to local vendor directory (equivalent of downloading node_modules locally)
$ go mod vendor
# publishing a module:
# Note: Go doesn't have an index of repositories like NPM.
# Go modules are hosted as public git repositories.
# To publish, simply push to the repository and tag releases.package main
import (
"fmt"
// importing a module
"github.com/go-shadow/moment"
)
func main() {
now := moment.New().Now().Unix()
fmt.Println(now)
}Output
1546595748package greeter
import (
"fmt"
)
// exporting a module (use a capitalized name to export function)
func Greet(name string) {
fmt.Printf("hello %s", name)
}package main
import (
// importing exported module
greeter "github.com/miguelmota/golang-for-nodejs-developers/examples/greeter_go"
)
func main() {
greeter.Greet("bob")
}Output
hello bobfunction foo() {
throw new Error('failed')
}
try {
foo()
} catch(err) {
console.trace(err)
}Output
Trace: Error: failed
at foo (/Users/bob/examples/stack_trace.js:2:9)
at Object.<anonymous> (/Users/bob/examples/stack_trace.js:6:3)
at Module._compile (internal/modules/cjs/loader.js:688:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:699:10)
at Module.load (internal/modules/cjs/loader.js:598:32)
at tryModuleLoad (internal/modules/cjs/loader.js:537:12)
at Function.Module._load (internal/modules/cjs/loader.js:529:3)
at Function.Module.runMain (internal/modules/cjs/loader.js:741:12)
at startup (internal/bootstrap/node.js:285:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:739:3)
at Object.<anonymous> (/Users/bob/examples/stack_trace.js:8:11)
at Module._compile (internal/modules/cjs/loader.js:688:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:699:10)
at Module.load (internal/modules/cjs/loader.js:598:32)
at tryModuleLoad (internal/modules/cjs/loader.js:537:12)
at Function.Module._load (internal/modules/cjs/loader.js:529:3)
at Function.Module.runMain (internal/modules/cjs/loader.js:741:12)
at startup (internal/bootstrap/node.js:285:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:739:3)package main
import (
"errors"
"fmt"
"runtime/debug"
)
func foo() {
panic(errors.New("failed"))
}
func main() {
defer func() {
if r := recover(); r != nil {
fmt.Println(string(debug.Stack()))
}
}()
foo()
}Output
goroutine 1 [running]:
runtime/debug.Stack(0xc000090eb8, 0x10a8400, 0xc00007e1c0)
/Users/mota/.gvm/gos/go1.11/src/runtime/debug/stack.go:24 +0xa7
main.main.func1()
/Users/bob/examples/stack_trace.go:16 +0x46
panic(0x10a8400, 0xc00007e1c0)
/Users/mota/.gvm/gos/go1.11/src/runtime/panic.go:513 +0x1b9
main.foo(...)
/Users/bob/examples/stack_trace.go:10
main.main()
/Users/bob/examples/stack_trace.go:20 +0xa2Example of creating a table, inserting rows, and reading rows from a sqlite3 database
const sqlite3 = require('sqlite3').verbose()
const db = new sqlite3.Database('./sqlite3.db')
db.serialize(() => {
db.run('CREATE TABLE persons (name TEXT)')
const stmt = db.prepare('INSERT INTO persons VALUES (?)')
const names = ['alice', 'bob', 'charlie']
for (let i = 0; i < names.length; i++) {
stmt.run(names[i])
}
stmt.finalize()
db.each('SELECT rowid AS id, name FROM persons', (err, row) => {
if (err) {
console.error(err)
return
}
console.log(row.id, row.name)
})
})
db.close()Output
1 'alice'
2 'bob'
3 'charlie'package main
import (
"database/sql"
"fmt"
_ "github.com/mattn/go-sqlite3"
)
func main() {
db, err := sql.Open("sqlite3", "./sqlite3.db")
if err != nil {
panic(err)
}
defer db.Close()
_, err = db.Exec("CREATE TABLE persons (name TEXT)")
if err != nil {
panic(err)
}
tx, err := db.Begin()
if err != nil {
panic(err)
}
stmt, err := tx.Prepare("INSERT INTO persons VALUES (?)")
if err != nil {
panic(err)
}
defer stmt.Close()
names := []string{"alice", "bob", "charlie"}
for _, name := range names {
_, err := stmt.Exec(name)
if err != nil {
panic(err)
}
}
tx.Commit()
rows, err := db.Query("SELECT rowid AS id, name FROM persons")
if err != nil {
panic(err)
}
defer rows.Close()
for rows.Next() {
var id int
var name string
err = rows.Scan(&id, &name)
if err != nil {
panic(err)
}
fmt.Println(id, name)
}
err = rows.Err()
if err != nil {
panic(err)
}
}Output
1 alice
2 bob
3 charlieconst test = require('tape')
test(t => {
const tt = [
{a:1, b:1, ret:2},
{a:2, b:3, ret:5},
{a:5, b:5, ret:10}
]
t.plan(tt.length)
tt.forEach(tt => {
t.equal(sum(tt.a, tt.b), tt.ret)
})
})
function sum(a, b) {
return a + b
}Output
$ node examples/example_test.js
TAP version 13
# (anonymous)
ok 1 should be equal
ok 2 should be equal
ok 3 should be equal
1..3
# tests 3
# pass 3
# okpackage example
import (
"fmt"
"testing"
)
func TestSum(t *testing.T) {
for _, tt := range []struct {
a int
b int
ret int
}{
{1, 1, 2},
{2, 3, 5},
{5, 5, 10},
} {
t.Run(fmt.Sprintf("(%v + %v)", tt.a, tt.b), func(t *testing.T) {
ret := sum(tt.a, tt.b)
if ret != tt.ret {
t.Errorf("want %v, got %v", tt.ret, ret)
}
})
}
}
func sum(a, b int) int {
return a + b
}Output
$ go test -v examples/example_test.go
=== RUN TestSum
=== RUN TestSum/(1_+_1)
=== RUN TestSum/(2_+_3)
=== RUN TestSum/(5_+_5)
--- PASS: TestSum (0.00s)
--- PASS: TestSum/(1_+_1) (0.00s)
--- PASS: TestSum/(2_+_3) (0.00s)
--- PASS: TestSum/(5_+_5) (0.00s)
PASS
ok command-line-arguments 0.008sconst Benchmark = require('benchmark')
const suite = new Benchmark.Suite
suite.add('fib#recursion', () => {
fibRec(10)
})
.add('fib#loop', () => {
fibLoop(10)
})
.on('complete', () => {
console.log(suite[0].toString())
console.log(suite[1].toString())
})
.run({
async: true
})
function fibRec(n) {
if (n <= 1) {
return n
}
return fibRec(n-1) + fibRec(n-2)
}
function fibLoop(n) {
let f = [0, 1]
for (let i = 2; i <= n; i++) {
f[i] = f[i-1] + f[i-2]
}
return f[n]
}Output
$ node examples/benchmark_test.js
fib#recursion x 1,343,074 ops/sec ±1.26% (84 runs sampled)
fib#loop x 20,104,517 ops/sec ±3.78% (78 runs sampled)package example
import (
"testing"
)
func BenchmarkFibRec(b *testing.B) {
for n := 0; n < b.N; n++ {
fibRec(10)
}
}
func BenchmarkFibLoop(b *testing.B) {
for n := 0; n < b.N; n++ {
fibLoop(10)
}
}
func fibRec(n int) int {
if n <= 1 {
return n
}
return fibRec(n-1) + fibRec(n-2)
}
func fibLoop(n int) int {
f := make([]int, n+1, n+2)
if n < 2 {
f = f[0:2]
}
f[0] = 0
f[1] = 1
for i := 2; i <= n; i++ {
f[i] = f[i-1] + f[i-2]
}
return f[n]
}Output
$ go test -v -bench=. -benchmem examples/benchmark_test.go
goos: darwin
goarch: amd64
BenchmarkFibRec-8 5000000 340 ns/op 0 B/op 0 allocs/op
BenchmarkFibLoop-8 30000000 46.5 ns/op 96 B/op 1 allocs/op
PASS
ok command-line-arguments 3.502s/**
* Creates a new Person.
* @class
* @example
* const person = new Person('bob')
*/
class Person {
/**
* Create a person.
* @param {string} [name] - The person's name.
*/
constructor(name) {
this.name = name
}
/**
* Get the person's name.
* @return {string} The person's name
* @example
* person.getName()
*/
getName() {
return this.name
}
/**
* Set the person's name.
* @param {string} name - The person's name.
* @example
* person.setName('bob')
*/
setName(name) {
this.name = name
}
}person.go
package person
import "fmt"
// Person is the structure of a person
type Person struct {
name string
}
// NewPerson creates a new person. Takes in a name argument.
func NewPerson(name string) *Person {
return &Person{
name: name,
}
}
// GetName returns the person's name
func (p *Person) GetName() string {
return p.name
}
// SetName sets the person's name
func (p *Person) SetName(name string) string {
return p.name
}person_test.go
// Example of creating a new Person.
func ExampleNewPerson() {
person := NewPerson("bob")
_ = person
}
// Example of getting person's name.
func ExamplePerson_GetName() {
person := NewPerson("bob")
fmt.Println(person.GetName())
// Output: bob
}
// Example of setting person's name.
func ExamplePerson_SetName() {
person := NewPerson("alice")
person.SetName("bob")
}Pull requests are welcome!
Please submit a pull request for new interesting additions or for general content fixes.
If updating code, update both the README and the code in the examples folder.
Released under the MIT license.
