Extend an object with the "has own property"'s of other object(s)

  • xok

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002.0.07 years ago9 years agoMinified + gzip package size for xok in KB


NOTE: as it turns out, this library very closely matched the behavior of the new Object.assign builtin! (MDN documentation)
To celebrate, I've updated it to simply use the builtin implementation when available. So you can use this as a quasi-polyfill for Object.assign if you'd like, or just use Object.assign
Main differences:
  • xok doesn't check or convert its target to an object like Object.assign does
  • xok has a slightly different check for the validity of subsequent arguments

Simply extend an object with the keys from others.
The name is short for extend-object-ownkeys; hat tip to @henrikjoreteg for 'extend-object' which does pretty much the same thing as this, but uses for … in to match Underscore.js instead of Object.keys to match ???. See also 'extend' if you want all the $.extend features.


var extend = require('xok'),
    assert = function (ok) { if (!ok) throw Error(); };

// use for shallow copies
var sampleObj = {abc:123,def:42},
    shallowClone = extend({}, sampleObj);
assert('abc' in shallowClone);
shallowClone.def = 0;
assert(sampleObj.def === 42);

// or defaulting options!
function test(opts) {
    opts = extend({
        foo: true,
        bar: 'someDefault'
    }, opts);
    return (opts.foo) ? opts.bar : null;
assert(test() === 'someDefault');
assert(test({bar:'customValue'}) === 'customValue');
assert(test({foo:false}) === null);


  • extend = require('xok') — this module exports a single function.
  • extend(target, …) — returns target after going through all the following arguments and shallow-copying the objects' own properties into it. The extra arguments may be null (anything falsey really) but are otherwise expected to be objects and not strings or cheeses or wild animals or whatever.


Solipsistic Public License; see LICENSE file for details.