JavaScript Form Submit - Confirm or Cancel Submission Dialog Box

A simple inline JavaScript confirm would suffice:

<form onsubmit="return confirm('Do you really want to submit the form?');">

No need for an external function unless you are doing validation, which you can do something like this:

<script>
function validate(form) {

    // validation code here ...


    if(!valid) {
        alert('Please correct the errors in the form!');
        return false;
    }
    else {
        return confirm('Do you really want to submit the form?');
    }
}
</script>
<form onsubmit="return validate(this);">

You could use the JS confirm function.

<form onSubmit="if(!confirm('Is the form filled out correctly?')){return false;}">
  <input type="submit" />
</form>

http://jsfiddle.net/jasongennaro/DBHEz/

function show_alert() {
  if(!confirm("Do you really want to do this?")) {
    return false;
  }
  this.form.submit();
}