running time of referencing an array in javascript

Question

If I have a javascript array1 containing 10 000 items

what is the running time of:

 var array2=new array();
 array2.push(array1);

and what is the running time of

var object={};
object['array2']=array1;

are both O(n) ? thanks for explanation.

Might be more appropriate for programmers.stackexchange.com, where you're likely to get a more detailed, probably more scientific answer. — Michael Berkowski
– Michael Berkowski, Commented Dec 11, 2011 at 21:14
You should build your own test cases in jsperf.com. That's the only way to answer questions like this and then test it in the browsers you care about. — jfriend00
– jfriend00, Commented Dec 11, 2011 at 21:15
here's some interesting reading for you scottlogic.co.uk/2010/10/javascript-array-performance — evilone
– evilone, Commented Dec 11, 2011 at 21:17
@Michael: No. This is a specific question about a programming language. Much, much, much better than all the "fix my code for me plz" crap milling about; this is precisely the sort of question that should be on SO! — Lightness Races in Orbit
– Lightness Races in Orbit, Commented Dec 11, 2011 at 21:30

Matt Ball · Accepted Answer · 2011-12-11 21:15:25Z

3

They should both be amortized O(1) operations.

This (obviously) depends on the browser's JS implementation, but any sane one should use an arraylist-like implentation for []s, and a hashtable-like {}. Arraylists and hashtables both have amortized O(1) insert runtime.

answered Dec 11, 2011 at 21:15

Matt Ball

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2 Comments

bingjie2680 Over a year ago

is there arraylist and hashtable in javascript?

Matt Ball Over a year ago

[] is more-or-less an arraylist, and {} is more-or-less a hashtable.

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