var when = function(funcs){
    if(!(this instanceof when)){
        return new when(arguments);
    }
    this.funcs = Array.prototype.slice.call(funcs);
}
when.prototype = {
   then: function(then){
       var i = 0,
           funcs = this.funcs,
           l = funcs.length,
           results = [],
           // Custom Object replaces func when pass is called
           complete = {},
           // insure all functions have successfully completed
           // before calling then function
           try_then = function(){
               var i=0;
               // insure all functions have run
               while(i<l){
                   if(funcs[i++]!==complete)return;
               }
               then(results);
               // Prevent multiple calls to then
               then = function(){};
           }
       while(i<l)(function(i){
           var pass = function(result){
             results[i] = result
             funcs[i] = complete;
             try_then();
           }
           funcs[i](pass)
       })(i++);
   }
}

when(
    function(pass){
       setTimeout(pass,3000);
    },
    function(pass){
       pass('2nd');
    }
)
.then(function(results){
    console.log(results);
})