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Symbol-ES6

Provides support for ES6 Symbol API in ES5 for older JS environments i.e. older browsers or NodeJS.

ES6 Symbol polyfill in pure ES5.

Install

NPM

Install it from npm and require it before any other modules:

$ npm install --save symbol-es6

require("symbol-es6");

CDN

If you prefer CDN, then just insert it into your HTML page on the top of other scripts:

<script src="https://cdn.jsdelivr.net/npm/symbol-es6/dist/symbol-es6.min.js"></script>

Examples

"use strict";

var ES6 = require("symbol-es6");

console.log(Symbol("bar") === Symbol("bar")); //false

var sym = Symbol.for("bar");
var sym2 = Symbol("bar");

console.log(Symbol.for("bar") === sym); //true
console.log(sym === sym2); //false
console.log(Symbol.keyFor(sym)); //bar
console.log(Symbol.keyFor(sym2)); //undefined

console.log(Array.from("Hello")); //[ 'H', 'e', 'l', 'l', 'o' ]

var it = [1, 2].entries();

console.log(it.next()); //{ done: false, value: [ 0, 1 ] }
console.log(it.next()); //{ done: false, value: [ 1, 2 ] }
console.log(it.next()); //{ done: true, value: undefined }

it = [1, 2].keys();

console.log(it.next()); //{ done: false, value: 0 }
console.log(it.next()); //{ done: false, value: 1 }
console.log(it.next()); //{ done: true, value: undefined }

function Bar() {
}
console.log(Object.prototype.toString.call(new Bar())); //[object Object]

Bar.prototype[Symbol.toStringTag] = "Bar";

console.log(Object.prototype.toString.call(new Bar())); //[object Bar]

it = "Bar"[Symbol.iterator]();

console.log(it.next()); //{ done: false, value: 'B' }
console.log(it.next()); //{ done: false, value: 'a' }
console.log(it.next()); //{ done: false, value: 'r' }


console.log(ES6.isSymbol({})); //fasle
console.log(ES6.isSymbol(sym)); ///true

function Baz() {

}
console.log(ES6.instanceOf(89, Baz)); //false
Object.defineProperty(Baz, Symbol.hasInstance, {
   value: function (value) {
       return typeof value === "number";
   }
});
console.log(ES6.instanceOf(89, Baz)); //true

ES6.forOf([1, 2], function (v) {
    console.log(v);
});
//1
//2

console.log(ES6.spreadOperator([]).spread("Bar").array()); //[ 'B', 'a', 'r' ]

function TestSpread() {
    return Array.prototype.reduce.call(arguments, function (acc, currvalue) {
        return acc + currvalue;
    }, 0);
}

console.log(ES6.spreadOperator(TestSpread).spread([1, 2, 3, 4, 5]).call()); //15

function Student(name, roll) {
    this.name = name;
    this.roll = roll;
}

console.log(ES6.spreadOperator(Student).spread(["Ariyan", 10]).new().name); //Ariyan

Polyfills

Limitation

Some ES6 features can’t be implemented in ES5 natively like spread operator, for..of loop, ES6 version of instanceOf operator etc. So this module exports a object named ES6 globally, that provides some approximate equivalent implementation of those features.

ES6 Object

This object provides,