After much testing in the latest browsers (FF 7, IE 9, Safari 5, Chrome 15, and Opera 11.5) and with many strings, this is the implementation I’ve come up with. It is often faster than trim12, and is MUCH faster when there are more than a few spaces at the end of the string.

var trimN;
if(window.navigator.mozIsLocallyAvailable) //Firefox
//Firefox is faster this way. So is Safari but I can’t reliably detect it.
trimN = function (str) {
str = str.match(/\S+(?:\s+\S+)*/);
return str ? str[0] : “”;
}
else //other browsers
trimN = function (str) {
str = str.replace(/^\s+/, “”);
if(!str) return “”;
str = str.match(/^[\s\S]*\S(?=\s*$)/);
return str ? str[0] : “”;
}

This is only in Firefox, however.

Original length: 27661
trim1: 2ms (length: 27657)
trim2: 1706ms (length: 27654)
trim3: 1809ms (length: 27654)
trim4: 1322ms (length: 27654)
trim5: 724ms (length: 27654)
trim6: 9155ms (length: 27654)
trim7: 7107ms (length: 27654)
trim8: 4084ms (length: 27654)
trim9: 2436ms (length: 27654)
trim10: 12ms (length: 27654)
trim11: 491ms (length: 27654)
trim12: 431ms (length: 27654)

Thanks for the great post.

What I did to test it:

Went to your benchmark page > opened Firebug > right-clicked on the containing script tag > selected “Edit HTML” > replaced trim1′s code with the following function’s code block.

…..function trimN() {
……….var f = 0, t = str.length – 1;
……….while (str.charAt(f) === ‘ ‘) { ++f; }
……….while (str.charAt(t) === ‘ ‘) { –t; }
……….return str.slice(f, t);
…..}

Result: 0ms