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                <!DOCTYPE html>
<html lang="en">
  <title>Second example of an event listener</title>
    <meta charset="utf-8">
  <button id="myButton">Click me!</button>
    // instead of using the addEventListener method directly, we used it on a DOM object (the button)
    //  Get a reference of the HTML element that can fire the events you want to detect. This is done
    // using the DOM API that we'll   cover in detail later this week. In this example we used one of 
    // the most common/useful methods: var b = document.querySelector("#myButton");
    var b = document.querySelector("#myButton");
    // Call the addEventListener method on this object. In the example: b.addEventListener('click', callback)
    // Every DOM object has an addEventListener method. Once you get a reference of  any HMTL element from 
    // JavaScript, you can start listening to events on it.
    b.addEventListener('click', function(evt) {
      alert("Button clicked");