Jonathan Weiß

For the most of us, Monday is the beginning of a new working week. Often you feel a bit slow and sleepy (especially if you have a case of Mondays ;-) ).
But having a slow developer in front of the screen does not mean that your code has to be slow as well. So, I started the series Optimization Monday which will include one small, but effective hint for optimizing and speeding up your JavaScript code on each month's first Monday.

Today's hint is: prevent lookups.
Every word in your object chain has to be found in the interpreter's lookup table. You can shorten the chain by using a local variable which holds a reference to your target.

So, instead of

for(i=0; i<100; i++){
  Initech.Web.Framework.WebsuiteObjects.Counter.increase(i);
}

write this:

var incr = Initech.Web.Framework.WebsuiteObjects.Counter.increase;
for(i=0; i<100; i++){
  incr(i);
}

If you are using DOM functions, the advantage of using a reference will be even greater.

Slow:

document.body.childNodes[8].firstChild.childNodes[3].nodeValue = 'foo';
document.body.childNodes[8].firstChild.childNodes[6].nodeValue = 'bar';
document.body.childNodes[8].firstChild.childNodes[8].nodeValue = '42';

Faster:

var elem = document.body.childNodes[8].firstChild;
elem.childNodes[3].nodeValue = 'foo';
elem.childNodes[6].nodeValue = 'bar';
elem.childNodes[8].nodeValue = '42';