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The “change” event
Working with DOM3/23
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  • 1. What are you planning to do?
  • 2. The “change” event
  • 3. How the “change” event works
  • 4. Deleting the element from the list
  • 5. How to check the collection length
  • 6. Debugging the code
  • 7. Static and live collections
  • 8. Displaying the message on the page
  • 9. The “submit” event
  • 10. Cancelling the form submission
  • 11. How to obtain text from the input field
  • 12. Templates and the <template> tag
  • 13. The contents of the <template> tag, document-fragment
  • 14. Cloning and inserting elements, part 1
  • 15. Cloning and inserting elements, part 2
  • 16. Cloning and inserting elements, part 3
  • 17. Cloning and inserting elements, part 4
  • 18. How to clone elements
  • 19. Adding a new element to a list
  • 20. Deleting a new task in the list
  • 21. Clearing the input field
  • 22. Summary of “Actions with DOM”
  • 23. The third program: “Instant messenger”
Deleting the element from the list
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How the “change” event works

We added a function and placed a handler, and all that we have left to do is check how the change event handler works.

Call the addCheckHandler function from the loop for each element in the items collection.

Please note that the change event is triggered when the checkbox status is changed. This means that if the field is selected and we remove the checkmark from it, the event will also be triggered.

In the course of working on the to-do list, we will constantly refer to DOM API methods. We already know what DOM is. Take, for example, this assignment. What is an API? This is a group of methods that allow us to interact with a certain part of a program or interface. In the case of the DOM API, these are all the methods that allow us to do something with the DOM elements.

In our app, various DOM API methods will come in useful for us. These include not only querySelector and addEventListener (yes, these are also DOM API methods). We will learn about other methods in the following assignments.

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  • index.html
  • style.css
  • script.js
HTML
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <title>The To-Do List</title> <link href="style.css" rel="stylesheet"> </head> <body> <h1 class="visually-hidden">The To-Do List</h1> <ul class="todo-list"> <li class="todo-list-item"> <label> <input class="todo-list-input" type="checkbox"> <span>Feed the cat</span> </label> </li> <li class="todo-list-item"> <label> <input class="todo-list-input" type="checkbox"> <span>Leave the country</span> </label> </li> <li class="todo-list-item"> <label> <input class="todo-list-input" type="checkbox"> <span>Go for a run</span> </label> </li> </ul> <p class="empty-tasks hidden">All of the tasks have been completed. There are no new tasks.</p> <form class="add-form" action="https://echo.htmlacademy.ru/courses" method="post"> <input class="add-form-input" type="text" aria-label="Task description" placeholder="For example, buy an elephant" required> <button class="add-form-button" type="submit">Add new task</button> </form> <template id="task-template"> <li class="todo-list-item"> <label> <input type="checkbox" class="todo-list-input"> <span></span> </label> </li> </template> <script src="script.js"></script> </body> </html>
CSS
@font-face { font-weight: 400; font-family: "Muller"; font-style: normal; font-display: swap; src: url("fonts/Muller.woff") format("woff"); } body { margin: 40px 32px; font-size: 18px; line-height: normal; font-family: "Muller", sans-serif; } .visually-hidden, .todo-list-input { position: absolute; width: 1px; height: 1px; margin: -1px; padding: 0; overflow: hidden; white-space: nowrap; border: 0; clip: rect(0 0 0 0); clip-path: inset(100%); } .hidden { display: none; } .todo-list { margin: 0; padding: 0; list-style: none; } .todo-list-item { margin-bottom: 12px; } .todo-list-item label { display: block; padding: 12px 18px; background-color: #ffffff; border-radius: 4px; box-shadow: 0 2px 5px rgba(0, 0, 0, 0.15); cursor: pointer; user-select: none; } .todo-list-item span { display: flex; align-items: center; } .todo-list-input + span::before { content: ""; display: inline-block; width: 16px; height: 16px; margin-right: 16px; background-color: #ffffff; border: 2px solid #69b253; border-radius: 4px; } .todo-list-input:checked + span::before { background-color: #69b253; background-image: url("check-white.svg"); background-repeat: no-repeat; background-position: center; } .todo-list-input:not(:checked):hover + span::before, .todo-list-input:not(:checked):focus + span::before { background-color: rgba(105, 178, 83, 0.2); } .empty-tasks { color: #69b253; } .empty-tasks::before { content: ""; width: 14px; height: 13px; margin-right: 13px; background-image: url("check-green.svg"); background-repeat: no-repeat; background-position: center; } .add-form { display: flex; } .add-form-input { flex-grow: 1; box-sizing: border-box; height: 46px; margin-right: 16px; padding: 12px; font: inherit; border: 1px solid #a1b5c4; border-radius: 4px; } .add-form-input:focus { border: 1px solid #69b253; outline: none; } .add-form-input:hover { box-shadow: 0 0 6px rgba(105, 178, 83, 0.6); } .add-form-input::placeholder { color: #a1b5c4; } .add-form-button { flex-shrink: 0; padding: 12px; font: inherit; color: #ffffff; background-color: #69b253; border: none; border-radius: 4px; user-select: none; touch-action: manipulation; } .add-form-button:hover, .add-form-button:focus { background-color: #5aa045; outline: none; } .add-form-button:active { background-color: #42862e; }
JavaScript
var list = document.querySelector('.todo-list'); var items = list.querySelectorAll('.todo-list-item'); var addCheckHandler = function (item) { var checkbox = item.querySelector('.todo-list-input'); checkbox.addEventListener('change', function () { console.log('Goal achieved!'); }); }; for (var i = 0; i < items.length; i++) { console.log(items[i]); }

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Console
Goalscompleted
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    1. Inside the loop, replace the console output for the current element with the addCheckHandler function call. Pass the current element in the items collection to the function.
    2. Double-click on any target in the mini-browser and look at the console.

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