unshift vs push

@bsnoteOct 29.2009

Which of these array methods is less expensive?

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@rnd_meOct 29.2009 — #

[CODE]r=[1,2,3];
 r[r.length]=4;
 [/CODE]

is about 30% faster in IE than push...

@bsnoteauthorOct 29.2009 — #Hi rnd_me,

Thanks for this.

I encountered performance problems. Currently I use unshift method to add items to the beginning of the buffer. But it seems there is more efficient way.

It is more appropriate to ask: what is the most efficient way to add items to an array (no matter, in the beginning or in the end)?

@rnd_meOct 29.2009 — #Hi rnd_me,

Thanks for this.

I encountered performance problems. Currently I use unshift method to add items to the beginning of the buffer. But it seems there is more efficient way.

It is more appropriate to ask: what is the most efficient way to add items to an array (no matter, in the beginning or in the end)?[/QUOTE]

i posted it...

it's quicker to go to the end, since adding to the front requires re-indexing the whole array...

it a tightly controlled situation, you can get a 1-3% boost by using "++":

[CODE]var r=[1,2,3],[COLOR="Red"] mx[/COLOR]=r.length, ob={a:1,b:2};
 
 for(it in ob){
 r[[COLOR="Red"]mx++[/COLOR]]=ob[it];
 }[/CODE]

this example is not worth it, but for bigger workloads ++ can save a little time compared to using array.length...

note that in firefox and chrome, these tweaks make little difference.

I chalk that up to those browser's "early optimizations".

The do howver make a lot of difference for naive script engines like those in IE and Opera.

@bsnoteauthorOct 30.2009 — #This answers my question. Thanks rnd me.

unshift vs push

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