if (document.readyState === "complete")
            callback();
        else if (document.addEventListener)
        {
            document.addEventListener("DOMContentLoaded",callback,false);
            window.addEventListener("load",callback,false);
        }
        else if(window.attachEvent)
        {
            document.attachEvent("onreadystatechange", callback);
            window.attachEvent("onLoad",callback);
        } else
            setTimeout(callback,2000);

$(callback);

function bindReady(handler){
    var called = false
    function ready() {
        if (called) return
        called = true
        handler()
    }
    if ( document.addEventListener ) {
        document.addEventListener( "DOMContentLoaded", function(){
            ready()
        }, false )
    } else if ( document.attachEvent ) {
        if ( document.documentElement.doScroll && window == window.top ) {
            function tryScroll(){
                if (called) return
                if (!document.body) return
                try {
                    document.documentElement.doScroll("left")
                    ready()
                } catch(e) {
                    setTimeout(tryScroll, 0)
                }
            }
            tryScroll()
        }
        document.attachEvent("onreadystatechange", function(){
            if ( document.readyState === "complete" ) {
                ready()
            }
        })
    }
    if (window.addEventListener)
        window.addEventListener('load', ready, false)
    else if (window.attachEvent)
        window.attachEvent('onload', ready)
    /*  else  // use this 'else' statement for very old browsers :)
        window.onload=ready
    */
}
readyList = []
function onReady(handler) {
    if (!readyList.length) {
        bindReady(function() {
            for(var i=0; i<readyList.length; i++) {
                readyList[i]()
            }
        })
    }
    readyList.push(handler)
}

onReady(function() {
  // ...
})

(function(exports, d) {
  function domReady(fn, context) {

    function onReady(event) {
      d.removeEventListener("DOMContentLoaded", onReady);
      fn.call(context || exports, event);
    }

    function onReadyIe(event) {
      if (d.readyState === "complete") {
        d.detachEvent("onreadystatechange", onReadyIe);
        fn.call(context || exports, event);
      }
    }

    d.addEventListener && d.addEventListener("DOMContentLoaded", onReady) ||
    d.attachEvent      && d.attachEvent("onreadystatechange", onReadyIe);
  }

  exports.domReady = domReady;
})(window, document);

<script src="domready.js"></script>
<script>
  domReady(function(event) {
    alert("dom is ready!");
  });
</script>

function init(event) {
  alert("check the console");
  this.log(event);
}

domReady(init, console);