copy-loop vs. Array.slice (v7)

Revision 7 of this benchmark created by Behrooz on

Description

The performance difference between copying an array by hand and copying it by slicing it (completely). This is for short arrays.

updated

In previous revision, the For loop test did not have pre-set length like the While loop did. This might contribute to while loop being more performant for the wrong reasons :-)

This discrepancy is fixed in current revision.

Setup

var list = new Array( "a", "b", "c", "d", "e" );

Test runner

Ready to run.

Testing in
TestOps/sec
Slice
var copy = list.slice();
ready
For
var n = list.length;
var copy = new Array(n);

for( var i = 0; i < n; i ++ ) {
    copy[ i ] = list[ i ];
}
ready
While
var i    = -1;
var n    = list.length;
var copy = new Array( n );

while( ++ i < n ) {
    copy[ i ] = list[ i ];
}
ready
While Reversed
var i    = list.length;
var copy = Array( i );

while( -- i > 0 ) {
  copy[ i ] = list[ i ];
}
ready
Pointless Pushing
var i    = -1;
var n    = list.length;
var copy = new Array();

while( ++ i < n ) {
    copy.push( list[ i ] )
}
ready

Revisions

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