JavaScript and HTML form validation

Question

I tried to do a simple validation on a button, but when I click the button without entering anything it still goes to testValidation1.html instead of popping up the alert window.

<html>

<head>
</head>

<body>

      <form action="testValidation1.html">

         Parameter1 : 
          <input type = 'text' name = 'param1'/><br>

          <input type='submit' value = 'submit' onclick = 'return validateForm()'>
      </form>

      <script type="text/javascript">

      function validateForm() {
             var f1 = document.forms[0];
             var p1 = f1.param1;

             if(p1.value.length == 0) {

                alert('Plz enter parameters');
                p1.focus();
                return false;
             }  
     }

      </script>


</body>
</html>

I might be dumb, but should it perhaps be onclick = 'validateForm()' instead of onclick = 'return validateForm()'? — Phil Tune
– Phil Tune, Commented Nov 20, 2014 at 21:09
I test it in my localhost .. it works fine .. it always show the popup .. — IbrahimAsad
– IbrahimAsad, Commented Nov 20, 2014 at 21:12
@IbrahimAsad, sometimes it shows the alert window but as soon as I clicked ok button it redirects me to testValidate1 page which it shouldn't right. — Aamir
– Aamir, Commented Nov 20, 2014 at 21:19
It should Never redirect to the other page ... I test it with IE,chrome , Firefox .. and every time it show the popup to me . :) — IbrahimAsad
– IbrahimAsad, Commented Nov 20, 2014 at 21:22

Sam Greenhalgh · Accepted Answer · 2014-11-20 21:14:17Z

2

you might find it easier to use the submit event of the form to validate

function validateForm(event) {
    var form = this;
    var p1 = form.elements['param1'];
    if(p1.value.length === 0) {
        alert('Plz enter parameters');
        p1.focus();
        event.preventDefault();
        return false;
    }
}

document.getElementById('form').addEventListener('submit', validateForm);

http://jsfiddle.net/7j0usuam/

answered Nov 20, 2014 at 21:14

Sam Greenhalgh

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