form validation js code example

Example 1: javascript login validation

<html>
<body>
<form id="form1" runat="server">
    <div class="container">
        <div class="main">
            <h2>
                Javascript Login Form Validation</h2>
            <form id="form_id" method="post" name="myform">
            <label>
                User Name :</label>
            <input type="text" name="username" id="username" />
            <br><br>
            <label>
                Password :</label>
            <input type="password" name="password" id="password" />
            <input type="button" value="Login" id="submit" onclick="validate();" />
            </form>
        </div>
    </div>
    </form>
</html>
</body>

Example 2: javascript onsubmit form validation

//form.html
<!DOCTYPE html>
<html>
<head>
<title>Javascript Onsubmit Event Example</title>
<link href="css/style.css" rel="stylesheet"> <!-- Include CSS File Here-->
<script src="js/onsubmit_event.js"></script>
</head>
<body>
<div class="container">
<div class="main">
<form action="#" method="post" onsubmit="return ValidationEvent()">
<h2>Javascript Onsubmit Event Example</h2>
<label>Name :</label>
<input id="name" name="name" placeholder="Name" type="text">
<label>Email :</label>
<input id="email" name="email" placeholder="Valid Email" type="text">
<label>Gender :</label>
<input id="male" name="gender" type="radio" value="Male">
<label>Male</label>
<input id="female" name="gender" type="radio" value="Female">
<label>Female</label>
<label>Contact No. :</label>
<input id="contact" name="contact" placeholder="Contact No." type="text">
<input type="submit" value="Submit">
<span>All type of validation will execute on OnSubmit Event.</span>
</form>
</div>
</div>
</body>
</html>

//js/onsubmit_event.js
// Below Function Executes On Form Submit
function ValidationEvent() {
// Storing Field Values In Variables
var name = document.getElementById("name").value;
var email = document.getElementById("email").value;
var contact = document.getElementById("contact").value;
// Regular Expression For Email
var emailReg = /^([w-.]+@([w-]+.)+[w-]{2,4})?$/;
// Conditions
if (name != '' && email != '' && contact != '') {
if (email.match(emailReg)) {
if (document.getElementById("male").checked || document.getElementById("female").checked) {
if (contact.length == 10) {
alert("All type of validation has done on OnSubmit event.");
return true;
} else {
alert("The Contact No. must be at least 10 digit long!");
return false;
}
} else {
alert("You must select gender.....!");
return false;
}
} else {
alert("Invalid Email Address...!!!");
return false;
}
} else {
alert("All fields are required.....!");
return false;
}
}

Example 3: html form validation

<form action="">
    <label for="name">Username</label>
    <input id="name" type="text" required />
    <label for="Email">Email</label>
    <!-- The required attribute will prompt the user to make sure  -->
    <!-- the fields are not empty, and that the email is formatted correctly -->
    <!-- if you want to use custom validation you should use regex in JavaScript -->
    <input id="Email" type="text" required />
</form>

Example 4: javascript login validation

<script language = "JavaScript">
        function validate() {
            var username = document.getElementById("username").value;
            var password = document.getElementById("password").value;
            if (username == null || username == "") {
                alert("Please enter the username.");
                return false;
            }
            if (password == null || password == "") {
                alert("Please enter the password.");
                return false;
            }
            alert('Login successful');
            
        } 
</script>

Example 5: javascript form validation

<form name="myForm" action="/action_page.php" onsubmit="return validateForm()" 
method="post">

 Name: <input type="text" name="fname">

<input type="submit" value="Submit">

</form>

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