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.

Answer 1

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.