How to code the validation in javascript

Question

I'm very new to Javascript. I have done one template for login, It is working like a charm. Here My question is how to set up the validation and navigation like if(username==root && password==root) then it should redirect into other page. I just post my code. I didn't include the css code. Then i did this code in html in that i have try to write the javascript but i don't know how to handle this.

My code:

<!DOCTYPE html>
<html>
<style>
/* Full-width input fields */
input[type=text], input[type=password] {
    width: 100%;
    padding: 12px 20px;
    margin: 8px 0;
    display: inline-block;
    border: 1px solid #ccc;
    box-sizing: border-box;
}

/* Set a style for all buttons */
button {
    background-color: #0077B5;
    color: white;
    padding: 14px 20px;
    margin: 8px 0;
    border: none;
    cursor: pointer;
    width: 100%;
}

button:hover {
    opacity: 0.8;
}

/* Extra styles for the cancel button */
.cancelbtn {
    width: auto;
    padding: 10px 18px;
    background-color: #f44336;
}

/* Center the image and position the close button */
.imgcontainer {
    text-align: center;
    margin: 10px 0 5px 0;
    position: relative;
}

img.cisco{
    width: 30%;
    border-radius: 30%;
}

.container {
    padding: 10px;
}

span.psw {
    float: right;
    padding-top: 16px;
}

/* The Modal (background) */
.modal {
    display: none; /* Hidden by default */
    position: fixed; /* Stay in place */
    z-index: 1; /* Sit on top */
    left: 0;
    top: 0;
    width: 100%; /* Full width */
    height: 100%; /* Full height */
    /*overflow: auto;  Enable scroll if needed */
    background-color: rgb(0,0,0); /* Fallback color */
    background-color: rgba(0,0,0,0.4); /* Black w/ opacity */
    padding-top: 5px;
}

/* Modal Content/Box */
.modal-content {
    background-color: #fefefe;
    margin: 5% auto 15% auto; /* 5% from the top, 15% from the bottom and centered */
    border: 1px solid #888;
    width: 80%; /* Could be more or less, depending on screen size */
}

/* The Close Button (x) */
.close {
    position: absolute;
    right: 25px;
    top: 0;
    color: #000;
    font-size: 35px;
    font-weight: bold;
}

.close:hover,
.close:focus {
    color: red;
    cursor: pointer;
}

/* Add Zoom Animation */
.animate {
    -webkit-animation: animatezoom 0.6s;
    animation: animatezoom 0.6s
}

@-webkit-keyframes animatezoom {
    from {-webkit-transform: scale(0)} 
    to {-webkit-transform: scale(1)}
}

@keyframes animatezoom {
    from {transform: scale(0)} 
    to {transform: scale(1)}
}

/* Change styles for span and cancel button on extra small screens */
@media screen and (max-width: 200px) {
    span.psw {
       display: block;
       float: none;
    }
    .cancelbtn {
       width: 100%;
    }
    .Center {
  display: flex;
  align-items: center;
  justify-content: center;
}
}
</style>
<body>

<h2><text-align:center>Authentication Required</h2>

<button onclick="document.getElementById('id01').style.display='block'">Login</button>

<div id="id01" class="modal">

  <form class="modal-content animate" method="post" name="myform">
    <div class="imgcontainer">
      <span onclick="document.getElementById('id01').style.display='none'" class="close" title="Close Modal">&times;</span>
      <img src="../images/cisco1.png" alt="Cisco" class="cisco">
    </div>

    <div class="container">
      <label><b>Username</b></label>
      <input type="text" id="username" placeholder="Enter Username" name="uname" required>

      <label><b>Password</b></label>
      <input type="password" id="password" placeholder="Enter Password" name="psw" required>

      <button type="submit" id="login" onclick="validate()">Login</button>
      <input type="checkbox" checked="checked"> Remember me
    </div>

    <div class="container" style="background-color:#f1f1f1">
      <button type="button" onclick="document.getElementById('id01').style.display='none'" class="cancelbtn">Cancel</button>
      <span class="psw">Forgot <a href="#">password?</a></span>
    </div>
  </form>
</div>

<script>
    var attempt = 3; //Variable to count number of attempts

//Below function Executes on click of login button
function validate(){
    var username = document.getElementById("username").value;
    var password = document.getElementById("password").value;

    if ( username == "root" && password == "root"){
        alert ("Login successfully");
        console.log("Redirecting to welcome page...")
        window.location = "success_new.html"; //redirecting to other page
        return false;
    }
    else{
        attempt --;//Decrementing by one
        alert("You have left "+attempt+" attempt;");
        }

        //Disabling fields after 3 attempts
        if( attempt == 0){
            document.getElementById("username").disabled = true;
            document.getElementById("password").disabled = true;
            document.getElementById("submit").disabled = true;
            return false;
        }
}
</script>

</body>
</html>

Unless you are just playing around with this for practice, I would advice against validating credentials on the front-end because anyone could theoretically manipulate that validation. — Chris
– Chris, Commented Nov 6, 2017 at 13:04
Get the value by using document.getElementById and keep it in a var and then validate.I dont know what really you are facing difficulty in this — lalithkumar
– lalithkumar, Commented Nov 6, 2017 at 13:06
whatever now he has only name attributes in the form.he can add id or get the values by names — lalithkumar
– lalithkumar, Commented Nov 6, 2017 at 13:10
@Chris yeah i know but i have less time to report that's why i posted this question. thanks — Aroon
– Aroon, Commented Nov 6, 2017 at 13:11

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

At last I fix it. The issue here was "return" function on the onclick listener. here is that one

add return before the validate function

<button type="submit" id="login" onclick=" return validate()">Login</button>

Then it's works fine.

edited Jun 20, 2020 at 9:12

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11 silver badge

answered Nov 6, 2017 at 19:26

Aroon

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Comments

Feathercrown · Accepted Answer · 2017-11-06 14:36:24Z

0

var username = document.getElementById('uname');
var pwd = document.getElementById('psw');

document.getElementById("b").onclick = function(){
  if(username.value == "root" && pwd.value == "root"){
    console.log("Redirecting to welcome page...")
    window.location = "welcome.html";
  }
}

<h2 text-align:"center">Authentication Required</h2>

<button onclick="document.getElementById('id01').style.display='block';">Login</button>

<div id="id01" class="modal" style="display:none;">

  <form class="modal-content animate" action="">
    <div class="imgcontainer">
      <span onclick="document.getElementById('id01').style.display='none'" class="close" title="Close Modal">&times;</span>
      <img src="../images/logo1.png" alt="Logo" class="logo1">
    </div>

    <div class="container">
      <label><b>Username</b></label>
      <input type="text" placeholder="Enter Username" name="uname" id="uname" required>

      <label><b>Password</b></label>
      <input type="password" placeholder="Enter Password" name="psw" id="psw" required>

      <button type="button" id="b">Login</button>
      <input type="checkbox" checked="checked"> Remember me
    </div>

    <div class="container" style="background-color:#f1f1f1">
      <button type="button" onclick="document.getElementById('id01').style.display='none'" class="cancelbtn">Cancel</button>
      <span class="psw">Forgot <a href="#">password?</a></span>
    </div>
  </form>
</div>

<script>
// Get the modal
var modal = document.getElementById('id01');

// When the user clicks anywhere outside of the modal, close it
window.onclick = function(event) {
    if (event.target == modal) {
        modal.style.display = "none";
    }
}
</script>

Fixed it. If I were you, I'd go over these and look at each difference to see what went wrong. It should be noted that you shouldn't do client-side validation like this, because anyone can easily:

See the password and username
Go to the url directly
Etc.

You really should do this server-side.

edited Nov 6, 2017 at 14:36

answered Nov 6, 2017 at 13:42

Feathercrown

2,5911 gold badge19 silver badges32 bronze badges

4 Comments

Aroon Over a year ago

Oops . Not working for me. If i click the submit button it is not redirecting

Feathercrown Over a year ago

@ArunBaskar Try it now.

Aroon Over a year ago

please fix the issue. stackoverflow.com/questions/47137641/…

Feathercrown Over a year ago

What do you mean by "trying inside the script tag"?

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add return before the validate function

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