Question

I have a html form.

I want the user to be able to mark three checkboxes. If he marks more than three, I want to send an immediate warning message. How do I do this? (Never worked with JavaScript before).

Answer 1

Use jQuery. Here’s an example that checks all your individual checkbox groups:

$(document).ready(function(){
  $(":checkbox").change(function(){
    if ($("[name="+this.name+"]").filter(":checked").length>3) {
      alert("Warning! You've selected more than three options.");
    }
  });
});

Here’s an example with your code.