Ajax Performance

Lazy Function Definition

From Peter Michaux comes a great article on the Lazy Function Definition pattern for JavaScript, an efficient way to use functional language coolness to avoid potentially expensive conditional checks or global namespace pollution. For example:


var t;
function foo() {
   if (t) {
      return t;
   }
   t = new Date();
   return t;
}

becomes

var foo = function() {
   var t = new Date();
   foo = function() {
      return t;
   };
   return foo();
};


That’s so clean. Of course, this specific example isn’t hugely useful from a performance perspective, but Peter also provides a page scroll implementation that likely would have a tangible speed boost.