Merge two JavaScript objects

Extend a JavaScript object with the key/value pairs of another.

With the following helper, you can merge two objects into one new object:

function extend(obj, src) {
    for (var key in src) {
        if (src.hasOwnProperty(key)) obj[key] = src[key];
} return obj; }

// example
var a = { foo: true }, b = { bar: false };
var c = extend(a, b);

// { foo: true, bar: false }

This is typically useful when merging an options dict with the default settings in a function or a plugin.

If support for IE 8 is not required, you may use Object.keys for the same functionality instead:

function extend(obj, src) {
    Object.keys(src).forEach(function(key) { obj[key] = src[key]; });
    return obj;

This involves slightly less code and is a bit faster.