How to concatenate the properties of several JavaScript objects

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I am looking for the best way to "add" multiple JavaScript objects (associative arrays).

For example, given:

a = { "one" : 1, "two" : 2 };
b = { "three" : 3 };
c = { "four" : 4, "five" : 5 };

what is the best way to compute:

{ "one" : 1, "two" : 2, "three" : 3, "four" : 4, "five" : 5 }


ECMAscript 6 introduced Object.assign() to achieve this natively in Javascript.

The Object.assign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.

MDN documentation on Object.assign()

var o1 = { a: 1 };
var o2 = { b: 2 };
var o3 = { c: 3 };

var obj = Object.assign({}, o1, o2, o3);
console.log(obj); // { a: 1, b: 2, c: 3 }

Object.assign is supported in many modern browsers but not yet all of them. Use a transpiler like Babel and Traceur to generate backwards-compatible ES5 JavaScript.