#object-keys 
An Object.keys shim. Invoke its "shim" method to shim Object.keys if it is unavailable.
Most common usage:
var keys = Object.keys || require('object-keys');
Example
var keys = require('object-keys');
var assert = require('assert');
var obj = {
a: true,
b: true,
c: true
};
assert.deepEqual(keys(obj), ['a', 'b', 'c']);
var keys = require('object-keys');
var assert = require('assert');
/* when Object.keys is not present */
delete Object.keys;
var shimmedKeys = keys.shim();
assert.equal(shimmedKeys, keys);
assert.deepEqual(Object.keys(obj), keys(obj));
var keys = require('object-keys');
var assert = require('assert');
/* when Object.keys is present */
var shimmedKeys = keys.shim();
assert.equal(shimmedKeys, Object.keys);
assert.deepEqual(Object.keys(obj), keys(obj));
Source
Implementation taken directly from es5-shim, with modifications, including from lodash.
Tests
Simply clone the repo, npm install, and run npm test