module.js

Function.prototype.method = function(name, func)
{
   this.prototype[name] = func;
   return this;
};

String.method('deentityify', function()
{
   var entity = {
      quot: '"',
      lt: '<',
      gt: '>'
   };
   return function() {
      return this.replace(/&([^&;]+);/g,
         function(a,b) {
            var r = entity[b];
            return typeof r === 'string' ? r : a;
         }
      );
   }
} () );

alert('aaa'.deentityify());