es6-symbol

What is es6-symbol?

The es6-symbol npm package provides a polyfill for the Symbol type introduced in ECMAScript 6. It offers a way to create unique identifiers that can be used as property keys in objects without the risk of name clashes. This is particularly useful for creating private or special properties that should not interfere with other properties in the object.

What are es6-symbol's main functionalities?

Creating symbols

This feature allows the creation of symbols, which can be used as unique identifiers. The code sample demonstrates how to create a symbol using the es6-symbol package.

var symbol = require('es6-symbol');
var mySymbol = symbol('mySymbol');

Using symbols as property keys

Symbols can be used as property keys in objects. This code sample shows how to assign and access a property in an object using a symbol as the key.

var symbol = require('es6-symbol');
var mySymbol = symbol('mySymbol');
var obj = {};
obj[mySymbol] = 'value';
console.log(obj[mySymbol]); // 'value'

Well-known symbols

The package provides access to well-known symbols defined by the ECMAScript specification, such as Symbol.iterator. This code sample demonstrates how to access a well-known symbol.

var symbol = require('es6-symbol');
var iteratorSymbol = symbol.iterator;
console.log(typeof iteratorSymbol); // 'symbol'

Other packages similar to es6-symbol

core-js

core-js is a modular standard library for JavaScript, which includes polyfills for ECMAScript up to 2021. It covers a broader range of ECMAScript features compared to es6-symbol, including symbols. core-js is more comprehensive but might be overkill if you only need symbol functionality.

babel-runtime

babel-runtime provides a set of polyfills required for a full ES2015+ environment. It includes support for symbols among other features. Compared to es6-symbol, babel-runtime is part of the Babel ecosystem, making it a good choice if you're already using Babel for transpiling your JavaScript code.

README

es6-symbol

ECMAScript6 Symbol polyfill

Limitations

• Underneath it uses real string property names which can easily be retrieved (however accidental collision with other property names is unlikely)
• As it needs custom toString behavior to work properly. Original Symbol.prototoype.toString couldn't be implemented as specified, still it's accessible as Symbol.prototoype.properToString

Usage

If you want to make sure your environment implements Symbol, do:

require('es6-symbol/implement');

If you'd like to use native version when it exists and fallback to polyfill if it doesn't, but without implementing Symbol on global scope, do:

var Symbol = require('es6-symbol');

If you strictly want to use polyfill even if native Symbol exists (hard to find a good reason for that), do:

var Symbol = require('es6-symbol/polyfill');

API

Best is to refer to specification. Still if you want quick look, follow examples:

var Symbol = require('es6-symbol');

var symbol = Symbol('My custom symbol');
var x = {};

x[symbol] = 'foo';
console.log(x[symbol]); 'foo'

// Detect iterable:
var iterator, result;
if (possiblyIterable[Symbol.iterator]) {
  iterator = possiblyIterable[Symbol.iterator]();
  result = iterator.next();
  while(!result.done) {
    console.log(result.value);
    result = iterator.next();
  }
}

Installation

NPM

In your project path:

$ npm install es6-symbol

Browser

You can easily bundle es6-symbol for browser with modules-webmake

Tests

$ npm test