Vanilla JavaScript Stop Form Submit

Let's say we want to add form validation in JavaScript, first we need to stop the form from actually submitting.

We can do this very simply in JavaScript.

HTML Structure

<form onsubmit="return validate();" novalidate>
  <input type="text" name="name" id="name" placeholder="Your name?" required />
  <br /><br />
  <input type="text" name="leave" placeholder="Leave me" />
  <br /><br />
  <input type="submit" value="Send" />
</form>

As you can see we use the on submit function and say to return a function callback. Then we have two fields of we will validate the first one.

JavaScript Stop Submit

To stop the submit we use the following code:

function validate() {
  var name = document.getElementById('name');
  if (name && name.value) {
    return true;
  } else {
    alert('Please fill the name field');
    return false;
  }
}

We use the return values, either true or false, depending on whether someone filled out the name field.

We could even use event.preventDefault() on the onsubmit function, but this will cause any action not to go true.

That would work well if we plan an Ajax post, for instance.

You can find this example on Codepen.

View on Codepen.

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