(function( ) {

    if (window.addEventListener) window.addEventListener("load", init, false);
    else if (window.attachEvent) window.attachEvent("onload", init);

    function init() {

        for(var i = 0; i < document.forms.length; i++){
            var f = document.forms[i];
            var needsValidation = false;
            for(j = 0; j < f.elements.length; j++) {

                var e = f.elements[j];
                if (e.type != "text") continue;
                var pattern = e.getAttribute("pattern");
                var required = e.getAttribute("required") != null;
                if (required && !pattern){
                    pattern = "\\S";
                    e.setAttribute("pattern", pattern);
                }

                if (pattern){
                    e.onchange = validateOnChange;
                    needsValidation = true;
                }

            }

        	if (needsValidation) f.onsubmit = validateOnSubmit;
		}

    }

	function validateOnChange(){

        var textfield = this;                            
        var pattern = textfield.getAttribute("pattern"); 
        var value = this.value;
        if (value.search(pattern) == -1) textfield.className = "invalid";
        else textfield.className = "valid";

    }

    function validateOnSubmit( ){

        var invalid = false;  // Start by assuming everything is valid
        for(var i = 0; i < this.elements.length; i++){
            var e = this.elements[i];
            if (e.type == "text" && e.onchange == validateOnChange){
                e.onchange( ); // Invoke the handler to re-validate
                if (e.className == "invalid") invalid = true;
            }

        }

        if (invalid){
            alert("The form is incorrectly filled out.\n" +
                  "Please correct the highlighted fields and try again.");
            return false;

        }
    }
 })( );