Help me make Contact Name required in a Form?

[ChrisJ]

I have this Form that works successfully (I know it's not state-of-the-art).
I simply want to add code to make Contact Name field mandatory. Can you help me?
I don't know how much code I should post. Here's some:

<script type="text/javascript">
function checkemail(){
var str=document.myform.email_address.value;
var filter=/^([\w-]+(?:\.[\w-]+)*)@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$/i;
if (filter.test(str))
testresults=true;
else {
alert("Please input a valid email address!");
return false;
}
if(document.myform.agree.checked!=1) {
alert("Please check the box to agree to the Terms.");
return false;
}
if(document.myform.ans.value.toLowerCase()!="white") {
alert("Please answer security question correctly: Black or White?");
return false;
}
return true;
}
</script>

[Echo89]

People can overide the JS, you must do it on the PHP side of things. But you can add in a bit of JS too just for looks:

// Your form:
<form blah blah onsubmit="checkfields()"></form>

// Your JS
var contact_name_value = document.getElementById('#contact_name').value
if(contact_name_value == '') {
    alert("Please enter a contact name!");
    return false;
}

[IIM]

there are many ways to do this:-

• HTML5 has introduced a very useful attribute "required".If we add this attribute to any control(textbox,textarea...) ,then that field is mandatory.
  http://www.whatwg.org/specs/web-apps/current-work/multipage/common-input-element-attributes.html#attr-input-required

• traditional javascript validation

  <script>
  var contact_name_value = document.getElementById('contact_name').value;//# not required.Semi colon missing
  if(contact_name_value == '') {
      alert("Please enter a contact name!");
      return false;
  }
  </script>
  <form onsubmit="checkfields()">
  <input type="text" name="contact_number" id="contact_name">
  <input type="submit">
  </form>
  

It depends on browser compactibility.html5 is supported by all modern browsers(chrome,firefox...).for IE version must be IE10

[Echo89]

But again, people can easily overide these attributes and JS. You must also validate on PHP side.