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Pressing a key
Getting to know events8/25
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  • 1. Introduction to events
  • 2. How to add a handler
  • 3. How event handlers work
  • 4. Default actions
  • 5. Please pass the function
  • 6. Hiding the popup
  • 7. Pressing a key
  • 8. Choosing a key
  • 9. With one key press
  • 10. Summary of “Events in JavaScript”, part 1
  • 11. First program: “Don’t be shy”
  • 12. Welcome to our photo gallery
  • 13. Click ’em all!
  • 14. Adding an image
  • 15. A bug has crept into the system
  • 16. Scope
  • 17. Global scope
  • 18. Changing variables from outside
  • 19. Becoming Independent
  • 20. Closures
  • 21. Let’s prepare for school
  • 22. Fixing the gallery
  • 23. Getting to the heart of the matter
  • 24. Summary of “Events in JavaScript”, part 2
  • 25. The Second Program: “Señor Tomato”
With one key press
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Choosing a key

We added an event handler, and it runs when we press any key. But any key won’t do. We need to use ESC. How can we execute the code by pressing just one specific key? Let’s turn our attention to the event object, which we are already familiar with.

We previously mentioned that the event object has many useful properties. For example, the event type, entered character, the cursor coordinates at the time the event occurred, and much more. These also include the code of the key that the user pressed. This property is called keyCode.

This property gives a numeric code for the pressed key. For example, Enter has the code 13, whereas ESC has the code 27. We will use 27 to identify ESC in this example. You can read more about these key codes here.

We now know that we have the event object, which contains the code of the pressed key in the keyCode property, and we know the code of the desired key. The only thing left to do is compare these codes inside the handler.

document.addEventListener('keydown', function(evt) {
  // Let's check that the key code is equal to 27.
  if (evt.keyCode === 27) {
    // The code is only executed when ESC is pressed.
  }
});

Let’s configure our handler so that the instructions are executed only when ESC is pressed.

By the way,

there are other properties besides keyCode for determining the pressed key. There is key, for example. It is different due to the fact that it doesn’t return the key code, but rather its value as a string, such as “Enter”, “Alt”, and “Escape”. We also have the code property. It identifies the physical key on the keyboard. In this case, the selected keyboard language does not have any influence on the value. These properties are alternatives to the deprecated keyCode property. Choose the one that provides the information your program needs, and check support in your target browsers.

Comments

  • index.html
  • style.css
  • script.js
HTML
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <title>CandyShop</title> <link href="candy-shop/setting.css" rel="stylesheet"> <link href="style.css" rel="stylesheet"> </head> <body> <section class="card"> <div class="card__content"> <h1 class="visually-hidden">The CandyShop Ice Cream Parlor</h1> <img class="card__logo" src="candy-shop/candyshop.svg" width="205" height="63" alt="The CandyShop"> <p class="card__text">We make ice cream from the freshest cream!</p> <img class="card__img" src="candy-shop/icecream.png" width="196" height="240" alt="Ice cream"> </div> <div class="card__controls"> <a href="contacts.html" class="card__button button-open">Show contacts</a> </div> </section> <section class="modal modal--show"> <div class="modal__content"> <h2 class="visually-hidden">Contact us</h2> <h3>Address:</h3> <p>19/8 Bolshaya Konyushennaya, St. Petersburg, 191186</p> <h3>Phone:</h3> <p>+7 (812) 275-75-75</p> <h3>Email:</h3> <p>mail@htmlacademy.ru</p> <button class="modal__button button-close" type="button">Close</button> </div> </section> <script src="script.js"></script> </body> </html>
CSS
h3 { margin: 0.5em 0; } p { margin: 0.5em 0 2em; } .card { width: 420px; margin: 50px auto 0; } .card__content { position: relative; background-color: #fad400; display: flex; flex-direction: column; align-items: flex-start; padding-top: 15px; padding-left: 20px; box-shadow: 0 5px 8px 0 #e8e8e8; } .card__img { align-self: flex-end; margin-top: auto; } .card__logo { position: absolute; } .card__text { font-size: 16px; line-height: 22px; font-weight: bold; position: absolute; left: 20px; top: 100px; width: 190px; } .card__controls { display: flex; justify-content: center; align-items: center; border: 2px solid #e8e8e8; border-top: 0; border-bottom-right-radius: 10px; border-bottom-left-radius: 10px; padding-top: 20px; padding-bottom: 20px; } .card__button { border: 0; padding: 12px 0; width: 230px; text-transform: uppercase; text-align: center; border-radius: 50px; color: #ffffff; font-weight: bold; font-size: 16px; text-decoration: none; background-color: #fad400; } .card__button:hover, .card__button:focus { background-color: #82da03; } .card__button:active { color: rgba(255, 255, 255, 0.3); background-color: #6cb502; } .modal { display: none; position: absolute; top: 0; left: 0; width: 100%; height: 100%; } .modal--show { display: block; } .modal::after { content: ""; position: fixed; top: 0; left: 0; height: 100%; width: 100%; background-color: rgba(0, 0, 0, 0.3); z-index: 1; } .modal__content { position: relative; width: 300px; margin: 100px auto; padding: 30px 70px 15px; background-color: #ffffff; box-shadow: -1px 5px 12px 0 rgba(89, 90, 90, 0.3); z-index: 2; } .modal__button { position: absolute; top: 20px; right: 20px; width: 20px; height: 20px; font-size: 0; background: none; border: 0; } .modal__button::after, .modal__button::before { content: ""; position: absolute; right: 0; top: 20px; width: 26px; height: 6px; margin: -13px -3px; background-color: #7656de; } .modal__button::before { transform: rotate(45deg); } .modal__button::after { transform: rotate(-45deg); } .modal__button:hover::after, .modal__button:hover::before, .modal__button:focus::after, .modal__button:focus::before { background-color: #9b7ff7; } .modal__button:active::after, .modal__button:active::before { background-color: #4023a0; } .visually-hidden { position: absolute; width: 1px; height: 1px; margin: -1px; border: 0; padding: 0; white-space: nowrap; clip-path: inset(100%); clip: rect(0 0 0 0); overflow: hidden; }
JavaScript
var popup = document.querySelector('.modal'); var openPopupButton = document.querySelector('.button-open'); var closePopupButton = popup.querySelector('.button-close'); openPopupButton.addEventListener('click', function (evt) { evt.preventDefault(); popup.classList.add('modal--show'); }); closePopupButton.addEventListener('click', function () { popup.classList.remove('modal--show'); }); document.addEventListener('keydown', function () { console.log('I pressed some key'); });

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Goalscompleted
0
    1. Add the evt parameter to the keyboard event handler function.
    2. Check whether evt.keyCode is equal to 27 inside the handler.
    3. Delete the console output from the handler, and add the console output of the string 'I pressed ESC'to the if block.
    4. Set focus to the mini-browser, press ESC on the keyboard, and check the message in the console.

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