confirm password validation in javascript w3schools 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: password validation in javascript

var check = function() {
  if (document.getElementById('password').value ==
    document.getElementById('confirm_password').value) {
    document.getElementById('message').style.color = 'green';
    document.getElementById('message').innerHTML = 'matching';
  } else {
    document.getElementById('message').style.color = 'red';
    document.getElementById('message').innerHTML = 'not matching';
  }
}
let pattern = new RegExp("^(?=(.*[a-zA-Z]){1,})(?=(.*[0-9]){2,}).{8,}$"); //Regex: At least 8 characters with at least 2 numericals
    let inputToListen = document.getElementById('pass-one'); // Get Input where psw is write
    let valide = document.getElementsByClassName('indicator')[0]; //little indicator of validity of psw

    inputToListen.addEventListener('input', function () { // Add event listener on input
        if(pattern.test(inputToListen.value)){
            valide.innerHTML = 'ok';
        }else{
            valide.innerHTML = 'not ok'
        }
    });

Example 3: 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>