Private methods in a JavaScript ES6 class using an ES7 decorator
This decorator wraps a class with another, exposing only public and static methods and properties. Behind the scenes, it creates properties for public methods on the prototype of the wrapped class. The properties return proxied functions to the original instance.
It supports inheritance and prototype changes even after class definition.
npm install class-private-method-decorator --saveRequires babel with babel-plugin-transform-decorators-legacy plugin.
import { classWithPrivateMethods, privateMethod } from 'class-private-method-decorator'
@classWithPrivateMethods
class SomeClass {
publicMethod() {
return 1
}
publicMethodThatUsesAPrivateMethod() {
return 2 + this.privateMethod()
}
@privateMethod
privateMethod() {
return 3
}
}
const something = new SomeClass()
something.publicMethod() // => 1
something.privateMethod() // => TypeError: something.privateMethod is not a function
something.publicMethodThatUsesAPrivateMethod() // => 5Since this library creates a wrapper class, extending its prototype after definition needs an extra step of extending the original class' prototype. extendClassWithPrivateMethods takes care of that.
import EventEmitter from 'events'
import { classWithPrivateMethods, privateMethod, extendClassWithPrivateMethods } from 'class-private-method-decorator'
@classWithPrivateMethods
class SomeClass {
cancel() {
this.emit('cancel')
}
}
extendClassWithPrivateMethods(SomeClass, EventEmitter.prototype)
const instance = new SomeClass()
instance.on('cancel', () => {
console.log('cancelled!')
})
instance.cancel() // cancelled!The original instance with all the methods can be accessed by __origInstance property. Useful for debugging.
something.__origInstance.privateMethod() // => 3The original class as a property of the wrapper class.
@classWithPrivateMethods
class SomeClass {
}
SomeClass.__origClass // will return the unwrapped SomeClassnpm install
npm testMIT