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• Last Modified
• 26.11.2007

Prototype.js $A Fix

Problem Description: When applying Events to elements or window, Firefox throws up an error if page is still loading:

Error: $A is not defined

Source File: prototype.js Line: 79

I've been looking all over the Internet to find a solution, but it appears this bug was in prototype for a while and I could not find a fix for a long time.

After all, I've decided to look into code myself. First I moved declaration of $A function in front of the code - no luck.

Finally, after some thinking, I applied a patch, that WILL NOT ALLOW executing $A function if it's not initialized.

And it worked just fine !!! Although, I can't explain the origin of this problem, had no time to dig further.

Just grab the code and forget this problem ever existed :)

Prototype.js v 1.5.0/1.5.1 fix:

Function.prototype.bindAsEventListener = function(object) {
  var __method = this, args = $A(arguments), object = args.shift();
  return function(event) {
      if(typeof $A === 'function'){                  // <-- Added Firefox Fix
         return __method.apply(object, [( event || window.event)].concat(args).concat($A(arguments)));
      }
  }
}

// "Thanks to Dave for the hint!"
Function.prototype.bind = function() {
  var __method = this, args = $A(arguments), object = args.shift();
  return function() {
      if(typeof $A === 'function'){                  // <-- Added Firefox Fix
         return __method.apply(object, args.concat($A(arguments)));
      }
  }
}

Prototype.js v 1.6.0+ fix:

  bind: function() {
    if (arguments.length < 2 && arguments[0] === undefined) return this;
    var __method = this, args = $A(arguments), object = args.shift();
    return function() {
	   if(typeof $A === 'function'){                  // <-- Added Firefox Fix
	     return __method.apply(object, args.concat($A(arguments)));
	   }	
    }
  },

  bindAsEventListener: function() {
    var __method = this, args = $A(arguments), object = args.shift();
    return function(event) {
	  if(typeof $A === 'function'){                  // <-- Added Firefox Fix
	     return __method.apply(object, [event || window.event].concat(args));
	  }
    }
  },