Highlights of JavaScript — Form Validation and Event Handling

Highlights of JavaScript — Form Validation and Event Handling

To learn JavaScript, we must learn the basics.

To learn JavaScript, we must learn the basics.

In this article, we’ll look at the most basic parts of the JavaScript language.

We can add validation to select dropdown fields.

For example, we can write the following HTML:

<form onSubmit="return checkForSelection();">
  <select id="fruits">
    <option value="" selected="selected">
      SELECT A FRUIT</option>
    <option value="apple">apple</option>
    <option value="orange">orange</option>
    <option value="grape">grape</option>    
  </select>
  <br>
  <input type="submit" value="Submit Form">
</form>

And then add the following JavaScript:

const checkForSelection = () => {
  if (document.getElementById("fruits").selectedIndex === 0) {
    alert("Please select a fruit.");
    return false;
  }
}

We added a select element and when we click on Submit Form, the checkForSelection function is run.

We add the return keyword so that we stop the default submit behavior and let the checkForSelection run.

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