How does Symbol work on ES6?

Question

In the new Javascript specification Ecmascript (ES6) a new primitive type was created called Symbol() what use it is?

Answer 1

Symbol() is a new primitive. How Function, Object and Number.

What is special is that it generates something unique. A Symbol is always unique. Some say it generates tokens (for being unique), always different.

That is to say:

var a = Symbol(123);
var b = Symbol(123);
console.log(a == b, a === b); // false, false

es6fiddle: http://www.es6fiddle.net/ihpaffj0/

This is curiously true even in object property names.

var obj = {};
var a = obj[Symbol('prop')] = 'foo';
var b = obj[Symbol('prop')] = 'bar';
console.log(a, b, obj[Symbol('prop')]); // 'foo', 'bar', <vazio>

es6fiddle: http://www.es6fiddle.net/ihpapvuv/

Where it might be useful?

It’s hard to guess every use case, but some I imagine:

• generate Symbols unicos for ids and/or sessions
• avoid object property name bumps

Good reading ^{in English}

• Blog Axel Rauschmayer: http://www.2ality.com/2014/12/es6-symbols.html
• MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol