javascript onsubmit form validation

JavaScript
//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;
}
}<!DOCTYPE html>
<html>
<head>
<script>
function validateForm() {
  var x = document.forms["myForm"]["fname"].value;
  if (x == "") {
    alert("Name must be filled out");
    return false;
  }
}
</script>
</head>
<body>

<form name="myForm" action="/action_page.php" onsubmit="return validateForm()" method="post">
  Name: <input type="text" name="fname">
  <input type="submit" value="Submit">
</form>

</body>
</html>
Source