https://github.com/jokeyrhyme/js-sub-array-tests

tests to compare different methods of sub-prototyping Array
https://github.com/jokeyrhyme/js-sub-array-tests

Last synced: 21 days ago
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tests to compare different methods of sub-prototyping Array

• Host: GitHub
• URL: https://github.com/jokeyrhyme/js-sub-array-tests
• Owner: jokeyrhyme
• License: mit
• Created: 2013-05-13T13:27:47.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2016-12-16T04:15:10.000Z (almost 8 years ago)
• Last Synced: 2024-10-14T21:23:52.931Z (25 days ago)
• Language: JavaScript
• Size: 10.7 KB
• Stars: 1
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE-MIT

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README

        
# js_sub_array_tests

I put this together to test out some of the advice provided in this excellent

article:

http://perfectionkills.com/how-ecmascript-5-still-does-not-allow-to-subclass-an-array/

I wanted to see how much of this was still true, several years on. This advice

was also provided mostly for web browsers, and I wanted to see how Node.JS

affected the outcomes.

## Getting Started

You'll need the CLI module for [grunt](http://gruntjs.com) installed globally:

    npm install -g grunt-cli

In the project root, run:

    npm install

That will install the npm modules required for running the unit tests.

Once that's done, you can run the Node.JS unit tests with:

    grunt

or:

    grunt test

Additionally, you may run the browser-based tests with:

    grunt browser

although these tests are more interesting if actually opened in real browsers.

In fact, the PhantomJS + Mocha combination for these browser tests doesn't

really work that well in Node.JS, so grab a browser.

## Results

### Node.JS

- `grunt test` with Node.JS v0.10.5

- tests confirm Array-detectability, if manipulating length effects indices as

expected, and if manipulating indices effects length as expected

                | proper [[Class]] | length > indices | indices > length

--------------- | ---------------- | ---------------- | -----------

naive           | no               | yes              | no

stack           | no               | yes              | no

makeSubArray    | no               | yes              | yes

wrapper: direct | yes              | yes              | yes

This is quite different to @kangax's [original results](http://perfectionkills.com/how-ecmascript-5-still-does-not-allow-to-subclass-an-array/#summary).

I can only guess that V8 does things differently compared to the browser JavaScript engines that were used in the original comparision.

### Google Chrome

- browser tests run in Chromium 26

- same results as Node.JS

It isn't surprising the Chrome repeats the Node.JS results, as they both use V8.

### Mozilla Firefox

- browser tests run in Firefox 20

- same results as Node.JS

Firefox's JavaScript engine is a modern ECMAScript 5.1 engine, just like V8.

I'm starting to sense a pattern here.

### Internet Explorer

- browser tests run in Microsoft Internet Explorer 10

- same results as the others

## License

Copyright (c) 2013 Ron Waldon  

Licensed under the MIT license.