Using JavaScript to implement front-end form verification

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<! DOCTYPE html>  

 
<! DOCTYPE html>
 
Window.onload = function () {
	username =  document.getElementById ("username");
	Password = document.getElementById ("password");
	Password2 = document.getElementById ("Password2");
	email = document.getElementById ("Mail");
	Registerform = document.getElementById ("Registerform");

	Username.addeventlistener ("Blur", function () {
		validateusername ();
	Password.addeventlistener ("Blur", function () {
		validatepassword ();
	},false);
	Password2.addeventlistener ("Blur", function () {		
		validatePassword2 ();
		Issame (PASSWORD,PASSWORD2);
	},false);
	Email.addeventlistener ("Blur", function () {
		validatemail ();
	},false);
	Registerform.addeventlistener ("Submit", function (e) {
		if (Validateusername () &&validatepassword () &&validatepassword2 () &&validatemail ()
			&&issame (Password,password2)) {
			This.submit ();
		} else{
			Preventie (e);
		}
	},false);
})}
 

 
Determines whether the form is empty and conforms to a regular expression/directly by name to get Element function Getelementbymymethod (name) {return document.getElementById (name);}
	function Validateusername () {username = Getelementbymymethod ("username"); Return Isemptyandreg (username,/) ([a-z]|[
A-z]) \w{5,12}/);
	function ValidatePassword () {password = Getelementbymymethod ("password");
Return Isemptyandreg (password,/\s{6,12}/);
	function ValidatePassword2 () {password2 = Getelementbymymethod ("Password2");
Return Isemptyandreg (password2,/\s{6,12}/);
	function Validatemail () {email = Getelementbymymethod ("Mail");
Return Isemptyandreg (email,/\w+@\w+\.\w+/);
	function Isemptyandreg (obj,reg) {spanname = obj.id + "Tip";
		if (Obj.value = = "") {settipfailure (spanname);
	return false;
		}else if (reg.test (Obj.value)) {settipsuccess (spanname);
	return true;
		}else{settipfailure (spanname);
	return false;
	}//Determine if 2 passwords are the same function Issame (OBJ1,OBJ2) {if (Obj1.value = = Obj2.value) return true;
		else{Setisnosame ();
	return false; }//settingsThe corresponding prompt information function setisnosame () {//obj is the variable of the corresponding span objspan = document.getElementById ("Password2tip");
Objspan.innertext= "two times password is not the same";
	//Set the appropriate prompt information function settipsuccess (objname) {Objspan = document.getElementById (objname);
Objspan.innerhtml= "<font color= ' green ' >√</font>";
	//Set the appropriate prompt information function settipfailure (objname) {Objspan = document.getElementById (objname);
Objspan.innerhtml= "<font color= ' red ' >x</font>"; }//block browser behavior action function Preventie (e) {if (e && e.preventdefault) {//Now is the Consortium standard E.preventdefault ();//block Browser action}els e{Window.event.returnValue = false;//specifically for IE browser processing}}