Why Do ES6 Object Methods Work Without the 'function' Keyword?

How does this object method definition work without the "function" keyword?

Overview

This question delves into an intriguing code snippet that defines an object method without using the "function" keyword. Understanding this syntax requires delving into ES6's introduction of a shorthand notation for defining methods.

Question

Why does the following code snippet work in some browsers, despite omitting the "function" keyword?

var module = {
    foobar(arg1) {
        alert(arg1);
    }
};

module.foobar("Hello World");

Answer

The answer lies in ES6's introduction of a shorthand notation for defining object methods. According to the ECMAScript 2015 specification:

"A property of an object can also refer to a function or a getter or setter method."

var o = {
  property: function ([parameters]) {},
  get property() {},
  set property(value) {},
};

ES6 introduced a shorthand notation that removes the necessity of the "function" keyword:

// Shorthand method names (ES6)
var o = {
  property([parameters]) {},
  get property() {},
  set property(value) {},
  * generator() {}
};

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