What's the Mystery Behind JavaScript's `{a, b, c}` Object Literal Shorthand?

An Alternative Look at Object Literals: Delving into the Enigma of {a, b, c}

Recent developments in JavaScript have introduced the enigmatic object literal property value shorthand syntax, particularly exemplified by the intriguing structure {a, b, c}. This snippet presents an intriguing departure from the familiar var g = {a: g, b: b, c: c} pattern.

Examining the Construct

To elucidate the nature of {a, b, c}, let's refer to the given JavaScript code snippet:

var a = 1, b = 'x', c = true;

var d = {a: a, b: b, c: c}; // Object literal
var e = [a, b, c]; // Array
var f = {a, b, c}; // Object literal property value shorthand

Interestingly, all three variable declarations yield identical output when their values are inspected using alert():

alert(d.a  + ', ' + d.b +  ', ' + d.c ); // Output: 1, x, true
alert(e[0] + ', ' + e[1] + ', ' + e[2]); // Output: 1, x, true
alert(f.a  + ', ' + f.b +  ', ' + f.c ); // Output: 1, x, true

Unveiling the Mystery

Introduced with ECMAScript 2015, the {a, b, c} syntax is a concise shorthand for var f = {a: a, b: b, c: c}. This shorthand notation, also referred to as property value shorthand, enables developers to streamline object literal definitions.

Moreover, it allows for seamless integration with traditional property initialization syntax:

var f = {a: 1, b, c};

In this instance, the property a is initialized explicitly with the value 1, while b and c utilize the shorthand notation.

For a deeper dive into the concept, refer to the documentation on Property definitions in Object initializer.

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