Do loops check the array.length every time when comparing i against array.length?

Question

I was browsing around and I found this:

var i, len;
for(i = 0, len = array.length; i < len; i++) {  
   //...
}

My first thoughts are:

Answer 1

Here are a number of performance tests for different approaches

http://www.websiteoptimization.com/speed/10/