HTML Academy
Displaying the message on the page
Working with DOM9/23
Back to the list of tasks
  • 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”
Cancelling the form submission
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  • Theory
  • Comments

The “submit” event

We managed to display a message. Now let’s figure out how to add a task:

  • A task is considered completed and disappears if the user clicks the checkbox.
  • If all of the tasks are completed, then a message should be displayed informing the user that there are no more tasks.
  • If a new task is added to an empty list, the message disappears.
  • To add a new task, you must enter a description in the input field and press “Add task”. The task will then appear at the end of the list.

The task is added using the form, which consists of an input field and a button. The user must write the task text and then click the button. As a result, the task is added to the list. It is not added itself. It needs some assistance.

Take a look at the markup. The button attribute is located inside the submit form. This means that clicking it will cause data from the form to be sent to the server.

You can set up a function to catch the clicks on this button to add a task. However, there is a more universal approach: use the submit special event. It is triggered every time that the form is submitted. This event is universal because sometimes the form can be submitted not just by clicking on a button, but by pressing a certain key. For example, “Enter”.

Find the form in the markup, add the submit event handler to it, and make sure that the event is triggered.

The user can try to submit the form without completing the field. Usually, the contents of the fields on this form will be verified in order to make sure that the form is not submitted “empty.” But this is not what we will do. Our web designer added the required attribute to the field. It makes entering the text in the field mandatory. The form submission event is triggered only when there is some sort of string in this field.

Comments

  • 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"> </ul> <p class="empty-tasks">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.children; var emptyListMessage = document.querySelector('.empty-tasks'); var toggleEmptyListMessage = function () { if (items.length === 0) { emptyListMessage.classList.remove('hidden'); } }; var addCheckHandler = function (item) { var checkbox = item.querySelector('.todo-list-input'); checkbox.addEventListener('change', function () { item.remove(); toggleEmptyListMessage(); }); }; for (var i = 0; i < items.length; i++) { addCheckHandler(items[i]); } // Add an event handler here

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Console
Goalscompleted
0
    1. After the emptyListMessage variable, declare a variable newItemForm and write an element with the add-form class to it.
    2. At the end of the program, add the submit event handler to newItemForm.
    3. Inside the handler, output the 'Form submitted' string to the console.
    4. Enter Skip out on work in the input field, press the “Add new task” button, and look at the console output.

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