⛑️ JSON serialization should never fail.
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Prevent JSON.stringify() from:
- Throwing
- Changing types
- Filtering or transforming values unexpectedly
import safeJsonValue from 'safe-json-value'
const input = { one: true }
input.self = input
JSON.stringify(input) // Throws due to cycle
const { value, changes } = safeJsonValue(input)
JSON.stringify(value) // '{"one":true}"
console.log(changes) // List of changed properties
// [
// {
// path: ['self'],
// oldValue: <ref *1> { one: true, self: [Circular *1] },
// newValue: undefined,
// reason: 'unsafeCycle'
// }
// ]npm install safe-json-valueThis package works in both Node.js >=18.18.0 and browsers.
This is an ES module. It must be loaded using
an import or import() statement,
not require(). If TypeScript is used, it must be configured to
output ES modules,
not CommonJS.
value any
options Options?
Return value: object
Makes value JSON-safe by:
- Omitting properties which would throw,
change type unexpectedly or
be filtered with
JSON.stringify() - Resolving properties which would change value with
JSON.stringify()
This never throws.
Object with the following properties.
Type: number
Default: 1e7
Big JSON strings can make a process, filesystem operation or network request
crash. maxSize prevents it by setting a maximum
JSON.stringify(value).length.
Additional properties beyond the size limit are omitted. They are completely removed, not truncated (including strings).
const input = { one: true, two: 'a'.repeat(1e6) }
JSON.stringify(safeJsonValue(input, { maxSize: 1e5 }).value) // '{"one":true}"Type: boolean
Default: false
If false, object/array properties are processed recursively. Please note that
cycles are not removed when this is true.
Object with the following properties.
Type: any
Copy of the input value after applying all the changes to make
it JSON-safe.
The top-level value itself might be changed (including to undefined) if it
is either invalid JSON or has a toJSON() method.
The value is not serialized to a JSON string. This allows choosing the
serialization format (JSON, YAML, etc.), processing the value, etc.
Type: Change[]
List of changes applied to value. Each item is an
individual change to a specific property. A given property might have multiple
changes, listed in order.
Type: Array<string | symbol | number>
Property path.
Type: any
Property value before the change.
Type: any
Property value after the change. undefined means the property was omitted.
Type: string
Reason for the change among:
- Exceptions:
"unsafeCycle","unsafeBigInt","unsafeSize","unsafeException","unsafeToJSON","unsafeGetter" - Invalid descriptors:
"descriptorNotWritable","descriptorNotConfigurable" - Unexpected types:
"unstableInfinite" - Filtered values:
"ignoredFunction","ignoredUndefined","ignoredSymbolValue","ignoredSymbolKey","ignoredNotEnumerable","ignoredArrayProperty" - Unresolved values:
"unresolvedToJSON","unresolvedClass","unresolvedGetter"
Type: Error?
Error that triggered the change. Only present if reason is
"unsafeException",
"unsafeToJSON" or
"unsafeGetter".
This is a list of all possible changes applied to make the value JSON-safe.
JSON.stringify() can throw on specific properties. Those are omitted.
const input = { one: true }
input.self = input
JSON.stringify(input) // Throws due to cycle
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"const input = { toJSON: () => ({ one: true, input }) }
JSON.stringify(input) // Throws due to infinite `toJSON()` recursion
JSON.stringify(safeJsonValue(input).value) // '{"one":true,"input":{...}}"const input = { one: true, two: 0n }
JSON.stringify(input) // Throws due to BigInt
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"const input = { one: true, two: '\n'.repeat(5e8) }
JSON.stringify(input) // Throws due to max string length
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"const input = {
one: true,
two: {
toJSON: () => {
throw new Error('example')
},
},
}
JSON.stringify(input) // Throws due to `toJSON()`
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"const input = {
one: true,
get two() {
throw new Error('example')
},
}
JSON.stringify(input) // Throws due to `get two()`
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"const input = new Proxy(
{ one: false },
{
get: () => {
throw new Error('example')
},
},
)
JSON.stringify(input) // Throws due to proxy
JSON.stringify(safeJsonValue(input).value) // '{}'const input = {}
Object.defineProperty(input, 'one', {
value: true,
enumerable: true,
writable: false,
configurable: true,
})
input.one = false // Throws: non-writable
const safeInput = safeJsonValue(input).value
safeInput.one = false // Does not throw: now writableconst input = {}
Object.defineProperty(input, 'one', {
value: true,
enumerable: true,
writable: true,
configurable: false,
})
// Throws: non-configurable
Object.defineProperty(input, 'one', { value: false, enumerable: false })
const safeInput = safeJsonValue(input).value
// Does not throw: now configurable
Object.defineProperty(safeInput, 'one', { value: false, enumerable: false })JSON.stringify() changes the types of specific values unexpectedly. Those are
omitted.
const input = { one: true, two: Number.NaN, three: Number.POSITIVE_INFINITY }
JSON.stringify(input) // '{"one":true,"two":null,"three":null}"
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"const input = [true, undefined, Symbol(), false]
JSON.stringify(input) // '[true, null, null, false]'
JSON.stringify(safeJsonValue(input).value) // '[true, false]'JSON.stringify() omits some specific types. Those are omitted right away to
prevent any unexpected output.
const input = { one: true, two: () => {} }
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }const input = { one: true, two: undefined }
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }const input = { one: true, two: Symbol() }
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }const input = { one: true, [Symbol()]: true }
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }const input = { one: true }
Object.defineProperty(input, 'two', { value: true, enumerable: false })
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }const input = [true]
input.prop = true
JSON.parse(JSON.stringify(input)) // [true]
safeJsonValue(input).value // [true]JSON.stringify() can transform some values. Those are resolved right away to
prevent any unexpected output.
const input = {
toJSON: () => ({ one: true }),
}
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }const input = { one: new Date() }
JSON.parse(JSON.stringify(input)) // { one: '2022-07-29T14:37:40.865Z' }
safeJsonValue(input).value // { one: '2022-07-29T14:37:40.865Z' }const input = { one: new Set([]) }
JSON.parse(JSON.stringify(input)) // { one: {} }
safeJsonValue(input).value // { one: {} }const input = {
get one() {
return true
},
}
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }const input = new Proxy(
{ one: false },
{
get: () => true,
},
)
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }is-json-value: Check if a value is valid JSONtruncate-json: Truncate a JSON stringguess-json-indent: Guess the indentation of a JSON stringerror-serializer: Convert errors to/from plain objects
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