verify input value in javascript code example

Example 1: how to set validation for email in javascript

<script language="javascript">

function checkEmail() {

    var email = document.getElementById('txtEmail');
    var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;

    if (!filter.test(email.value)) {
    alert('Please provide a valid email address');
    email.focus;
    return false;
 }
}</script>

Example 2: form validation for email in js

<script>  
function validateform(){  
var name=document.myform.name.value;  
var password=document.myform.password.value;  
  
if (name==null || name==""){  
  alert("Name can't be blank");  
  return false;  
}else if(password.length<6){  
  alert("Password must be at least 6 characters long.");  
  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>