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    <p>There are at least <strong>5</strong> (!) ways to clone an array:</p> <ul> <li>loop</li> <li>slice</li> <li>Array.from()</li> <li>concat</li> <li>spread operator, etc. <em>(so slow, forget it for now)</em> </li> </ul> <p>There has been a huuuge <a href="http://jsben.ch/#/wQ9RU" rel="noreferrer">BENCHMARKS thread</a>, providing following information:</p> <ul> <li><p>for <strong>blink</strong> browsers <code>slice()</code> is the fastest method, <code>concat()</code> is a bit slower, and <code>while loop</code> is 2.4x slower. </p></li> <li><p>for other browsers <code>while loop</code> is the fastest method, since those browsers don't have internal optimizations for <code>slice</code> and <code>concat</code>.</p></li> </ul> <p>This remains true in Jul 2016. </p> <p>Below are simple scripts that you can copy-paste into your browser's console and run several times to see the picture. They output milliseconds, lower is better.</p> <p><strong>while loop</strong></p> <pre><code>n = 1000*1000; start = + new Date(); a = Array(n); b = Array(n); i = a.length; while(i--) b[i] = a[i]; console.log(new Date() - start); </code></pre> <p><strong>slice</strong> </p> <pre><code>n = 1000*1000; start = + new Date(); a = Array(n); b = a.slice(); console.log(new Date() - start); </code></pre> <p>Please note that these methods will clone the Array object itself, array contents however are copied by reference and are not deep cloned.</p> <pre><code>origAr == clonedArr //returns false origAr[0] == clonedArr[0] //returns true </code></pre>
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    1. POJavascript fastest way to duplicate an Array - slice vs for loop
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    1. COwell done! This might be the best answer now. Would you be able to explain why the simple test done by lincolnk (it's the above answer http://stackoverflow.com/a/3978716/260080 ) gives out the opposite result, where `slice` is the faster than looping? I'm wondering if it's caused by the the type of elements in the array, in his test they were all numbers, in your are a mix of strings and objects.
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    2. COMarco, you are quite right, storing data of one type speeds up an array. Google has written this somewhere, but you can always check it out http://jsperf.com/new-array-vs-splice-vs-slice/25 yourself However, the biggest difference makes the concrete engine realisation. Algorithms evolve from build to build. On the other hand we can predict evolution when knowing the engine architecture. @lincolnk's benchmarking results look similar to those http://jsperf.com/new-array-vs-splice-vs-slice/11, October '10 is somewhere close to Chrome 19 and FireFox 10. Oh, slice is shorter to type then concat :)
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