537548 - Add Array.isArray

Status: RESOLVED DUPLICATE of bug 510537

(Core :: JavaScript Engine, enhancement)

Description

[Juriy "kangax" Zaytsev]

Array.isArray is specified in (now-finalized) ES5 (see 15.4.3.2) and is present in nightly WebKit, Opera 10.5 pre-alpha and latest builds of Chrome 4.

All of these native implementations are significantly faster than custom one, such as, for example:

Array.isArray = function isArray(o) { 
  Object.prototype.toString.call(o) === '[object Array]';
};

WebKit is up to 17 times faster, Opera — up to 5 times, etc.

Implementing Array.isArray in Mozilla could be beneficial for scripts and libraries that use helper similar to the above (Prototype.js and jQuery definitely have it, other libraries probably have it too).

Thank you.

Comment 1

[Juriy "kangax" Zaytsev]

Here's a simple test I used for performance comparison — http://yura.thinkweb2.com/jstests/native_vs_custom_Array_isArray_perf_test.html

And this looks like a relevant test suite for Array.isArray in V8 — http://code.google.com/p/v8/source/browse/branches/bleeding_edge/test/mjsunit/third_party/array-isarray.js?spec=svn3060&r=3060