Question

I was just wondering whether this snippet of Javascript is going to slow down my site:

$(function(){
 var realLink = location.href;
 $( "#nav a" ).each(
  function( intIndex ){
   String.prototype.startsWith = function(str){
    return (this.indexOf(str) === 0);
   }
   var pageLink = $(this).attr("href");

   if ( realLink.startsWith(pageLink) )
    $(this).parent().addClass("active");   
  }
 );
});

It only loops about 5-7 times, and I don’t have very much Javascript looping experience.

Answer 1

There’s nothing inherently wrong with this snippet, except that you’re constantly creating and assigning a function to String.prototype.startsWith in a loop. That, of course, is an unnecessary work, and should at least be:

$(function(){
 var realLink = location.href;
 String.prototype.startsWith = function(str){
   return (this.indexOf(str) === 0);
 };
 $( "#nav a" ).each(
  function( intIndex ){
   var pageLink = $(this).attr("href");
   if ( realLink.startsWith(pageLink) )
    $(this).parent().addClass("active");   
  }
 );
});

I also don’t see a need for intIndex argument there. It’s not used anywhere in a function.