It doesn't look like it is written in JavaScript.

if you type _now in the console, you only get

function now() { [native code] }

You usually only get that when you try to look at some built-in method where the inner-workings are invisible to the browser.

setTimeout
=>function setTimeout() { [native code] }

Has _.now done something with "native code" of the JavaScript engine?

It doesn't look like it is written in JavaScript.

if you type _now in the console, you only get

function now() { [native code] }

You usually only get that when you try to look at some built-in method where the inner-workings are invisible to the browser.

setTimeout
=>function setTimeout() { [native code] }

Has _.now done something with "native code" of the JavaScript engine?

• javascript
• browser
• underscore.js
• v8
• native-code

Share Improve this question Follow asked Jan 30, 2015 at 0:21 12527481252748 15.4k3434 gold badges117117 silver badges242242 bronze badges 1

• 1 It probably just uses the native function if it exist. Otherwise it provides an implementation for it. – Alxandr Commented Jan 30, 2015 at 0:25

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 7

By default _.now is just Date.now, except in environments that do not support it. Where Date.now isn't supported _.now will use this implementation instead (same goes for lodash)

_.now = function() {
   return (new Date()).getTime()
};

As your browser supports Date.now, _.now is just a proxy to the native implementation

---

Note: you can also make any of your functions appear as native in console by calling using Function.prototype.bind

function foo() {console.log('bar');}
var bar = foo.bind(null);

console.log(bar);
// => function () { [native code] }

Take a look at the underscore source code:

_.now = Date.now || function() {
  return new Date().getTime();
};

This means that it will use Date.now() if it exists, which is an internal function. Otherwise it will use new Date().getTime(), which is supported by all JavaScript engines.

It returns an integer timestamp for the current time. Useful for implementing timing/animation functions.

_.now(); => 1392066795351