Why is Array.prototype.push faster than variable declaration

Question

and found out that push in this case :

var a = [];
a.push([1,2,3]);
a.push(["a","b","c"]);

is faster than just declaring a with the subarrays inside :

var a = [
  [1,2,3],
  ["a","b","c"]
];

Could anyone please tell me why or point me in the right documentation?

Thanks

Which browser did you use? I just tried in Edge and the push came out 20% slower. — Kirk Larkin
– Kirk Larkin, Commented Aug 11, 2017 at 18:22
.push() Firefox 55 on Windows 10 came out 23% slower but Chrome 61 came out 75% faster (similar results). — Pluto
– Pluto, Commented Aug 11, 2017 at 18:42
@Pluto yeah, I wouldn't say I'm surprised but I would still love to read documentation or articles on the subject. Optimization is very important to me — Anthony N.
– Anthony N., Commented Aug 11, 2017 at 20:20
for me on Chrome 61 push is about 6.5 times faster too on jsperf.com, but slower on jsben.ch, so depends on how it's measured too — Slai
– Slai, Commented Oct 12, 2017 at 4:11

Mr Phoenix · Accepted Answer · 2017-08-11 18:27:50Z

1

For me declaring a with sub arrays went faster than push :)

I think it depends on computer's/device's components

answered Aug 11, 2017 at 18:27

Mr Phoenix

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1 Comment

I'm using Chrome 60.0.3112 / Windows 7 0.0.0