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    <p><strong>UPDATE: <a href="https://github.com/jsperf/jsperf.com/issues/18#issuecomment-113569132">Note that JSPref is currently down</a></strong></p> <p><em>(i have saved a copy of the test case, and will update the answer once JSPref is fixed / a successor is found)</em></p> <hr> <p>Hmm... maybe an overkill for the answer... but I created <a href="http://jsperf.com/object-vs-array-vs-native-linked-list">a test suite, precisely to explore these issues (and more)</a> (<a href="http://web.archive.org/web/20150907055636/http://jsperf.com/object-vs-array-vs-native-linked-list">archived copy</a>).</p> <p>And in that sense, you can see the performance issues in this 50+ test case tester (it will take a long time).</p> <p>Also as its name suggest, it explores the usage of using the native linked list nature of the DOM structure.</p> <p><a href="http://pic-o.com/blog/2011/12/divlinkedlist/">(Currently down, rebuilt in progress) More details on my blog regarding this</a>.</p> <p><strong>The summary is as followed</strong></p> <ul> <li>V8 Array is Fast, VERY FAST </li> <li>Array push / pop / shift is ~approx 20x+ faster than any object equivalent.</li> <li>Surprisingly <code>Array.shift()</code> is fast ~approx 6x slower than an array pop, but is ~approx 100x faster than an object attribute deletion.</li> <li>Amusingly, <code>Array.push( data );</code> is faster than <code>Array[nextIndex] = data</code> by almost 20 (dynamic array) to 10 (fixed array) times over.</li> <li><code>Array.unshift(data)</code> is slower as expected, and is ~approx 5x slower than a new property adding.</li> <li>Nulling the value <code>array[index] = null</code> is faster than deleting it <code>delete array[index]</code> (undefined) in an array by ~approx 4x++ faster.</li> <li>Surprisingly Nulling a value in an object is <code>obj[attr] = null</code> ~approx 2x slower than just deleting the attribute <code>delete obj[attr]</code></li> <li>Unsurprisingly, mid array <code>Array.splice(index,0,data)</code> is slow, very slow. </li> <li>Surprisingly, <code>Array.splice(index,1,data)</code> has been optimized (no length change) and is 100x faster than just splice <code>Array.splice(index,0,data)</code></li> <li>unsurprisingly, the divLinkedList is inferior to an array on all sectors, except <code>dll.splice(index,1)</code> removal (Where it broke the test system).</li> <li><strong>BIGGEST SURPRISE</strong> of it all [as jjrv pointed out], V8 array writes are slightly faster than V8 reads =O</li> </ul> <p><strong>Note:</strong> These metrics applies only to large array/objects which v8 does not "entirely optimise out". There can be very isolated optimised performance cases for array/object size less then an arbitrary size (24?). More details can be seen extensively across several google IO videos.</p> <p><strong>Note 2:</strong> These wonderful performance results are not shared across browsers, especially <code>*cough*</code> IE. Also the test is huge, hence i yet to fully analyze and evaluate the results : please edit it in =)</p> <p><strong>Updated Note (dec 2012):</strong> Google representatives have videos on youtubes describing the inner workings of chrome itself (like when it switches from a linkedlist array to a fixed array, etc), and how to optimize them. See <a href="https://www.youtube.com/watch?feature=player_detailpage&amp;v=XAqIpGU8ZZk#t=994s">GDC 2012: From Console to Chrome</a> for more.</p> <p><strong>Updated Note (feb 2013):</strong> Thx @badunk, for providing the video link at the exact point</p> <p><strong>Updated Note (june 2016):</strong> Thx @Benedikt, regarding array push performance difference in fixed / dynamic arrays.</p>
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    1. POWhat is the performance of Objects/Arrays in JavaScript? (specifically for Google V8)
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    1. COthis is a great overkill answer for sure
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    2. COdude... the Internet (and I) thank you for your awesome answer and test suite. You win lots of points. :)
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    3. CO@BMiner, just so happen to see the question, after having this done =)
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