Fastest way to duplicate an array in JavaScript - slice vs. 'for' loop

Question

In order to duplicate an array in JavaScript: which of the following is faster to use?

###Slice method

var dup_array = original_array.slice();
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Answer 1

As @Dan said "This answer becomes outdated fast. Use benchmarks to check the actual situation", there is one specific answer from jsperf that has not had an answer for itself: while:

var i = a.length;
while(i--) { b[i] = a[i]; }

had 960,589 ops/sec with the runnerup a.concat() at 578,129 ops/sec, which is 60%.

This is the lastest Firefox (40) 64 bit.

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@aleclarson created a new, more reliable benchmark.