Length equal 0 or new array

JavaScript performance comparison

Revision 4 of this test case created


It should test what is more efficient way to clear an array.

Creating NEW with:

a = [];

or make the length equal 0 like this :

a.length = 0;

NOTE : Those two methods are not equal in their behaviour! First one (a = []) will make all NEW array, and second one (a.length = 0) modify current one! I is very important if you HAVE other references to that array!

Preparation code

Benchmark.prototype.setup = function() {
    a = [1,2,3,4,5,6,7,7];

Test runner

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Testing in unknown unknown
Test Ops/sec
New array method
a = [];
length equal to 0 method
a.length = 0;
Defining length isn't like usual "resetting" value
a.randomProperty = 0  // see the performance difference with setting length
while(a.length > 0) a.pop()

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