[英]How to alert user to correct input fields in form validation using javascript?
[英]Javascript form validation for user account
我正在創建一個帳戶創建表單,並使用JavaScript對其進行驗證。 我希望可以得到一些修復和優化它的幫助。 它返回不正確的警報,並有其他一些問題。 歡迎任何改進,我感謝收到的任何建議。 謝謝
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Create an Accoount</title>
<script type="text/javascript">
function validateform() {
//vars
var username = document.forms["usercreate"]["username"].value;
var email = document.forms["usercreate"]["email"].value;
var pass1 = document.forms["usercreate"]["pass1"].value;
var pass2 = document.forms["usercreate"]["pass2"].value;
//null check
if(username = "") {
alert ("You forgot the user name");
return false;
}
if(email = "") {
alert ("You forgot the email address");
return false;
}
if(pass1 = "") {
alert ("You forgot a password address");
return false;
}
if(pass2 = "") {
alert ("You forgot a password address");
return false;
}
if (username.length < 3 || username.length > 15) {
alert("User name is too short (under 3) or too big (over 15)");
return false;
}
if (pass1 != pass2) {
alert ("Passwords don't match");
return false;
}
if (pass1.length < 4) {
alert ("Your is password is too short (under 4)");
return false;
}
//email check
var atpos=email.indexOf("@");
var dotpos=email.lastIndexOf(".");
if (atpos<1 || dotpos<atpos+2 || dotpos+2>=email.length) {
alert("Not a valid e-mail address");
return false;
}
}
</script>
</head>
<body>
<h1>Account Creation</h1>
<form name="usercreate" action="usercreate.php" method="post" onsubmit="return validateform();">
<p><label for="username">Pick a user name (must be at least three letters characters)<br />
<input type="text" name="username" value="username"/><br />
<label for="email">Enter your email address:<br />
<input type="text" name="email" value="email"/><br /> <!-- check this -->
<label for="pass1">Create a password: <br />
<input type="password" name="pass1" /><br />
<label for="pass2">Retype the password:<br />
<input type="password" name="pass2" /><br />
<input type="submit" value="Create Account"/><br />
</form>
</p></body>
</html>
最大的問題是您使用賦值運算符=
而不是比較運算符===
(或==
):
if(username = "") {
// should be
if (username === "") {
// (and similar for the other fields)
按照這種方式,您實際上將 username
更改為一個空字符串,然后if測試正在評估該表達式的結果,該表達式作為一個空字符串是“ falsy”,因此將永遠不會顯示相應的警報。
試試這個
function validateform() {
//vars
var username = document.forms["usercreate"]["username"].value;
var email = document.forms["usercreate"]["email"].value;
var pass1 = document.forms["usercreate"]["pass1"].value;
var pass2 = document.forms["usercreate"]["pass2"].value;
var isFilled=true;
var msg="";
//null check
if(username == "") {
msg+="You forgot the user name\n";
isFilled=false;
}
if(email == "") {
msg+="You forgot the email address\n";
isFilled=false;
}
if(pass1 == "") {
msg+="You forgot a password address\n";
isFilled=false;
}
//if(pass2 == "") {
//msg+="You forgot a password address\n";
//isFilled=false;
//}
if (username.length < 3 || username.length > 15) {
msg+="User name is too short (under 3) or too big (over 15)\n";
isFilled=false;
}
if (pass1 != pass2) {
msg+="Passwords don't match\n";
isFilled=false;
}
if (pass1.length < 4) {
msg+="Your is password is too short (under 4)\n";
isFilled=false;
}
//email check
var atpos=email.indexOf("@");
var dotpos=email.lastIndexOf(".");
if (atpos<1 || dotpos<atpos+2 || dotpos+2>=email.length) {
msg+="Not a valid e-mail address\n";
isFilled=false;
}
if(!isFilled) {
alert(msg);
}
return isFilled;
}
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