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JavaScript JavaScript and the DOM (Retiring) Responding to User Interaction Event Delegation

Vic Mercier
Vic Mercier
3,276 Points
Posted by Vic Mercier
Vic Mercier
3,276 Points

delegation

Is the event delegation is in link about event.target.

index.html 
<!DOCTYPE html>
<html>
    <head>
        <title>JavaScript and the DOM</title>
    </head>
    <link rel="stylesheet" href="style.css" />
    <body>
        <section>
            <h1>Making a Webpage Interactive</h1>
            <p>JavaScript is an exciting language that you can use to power web servers, create desktop programs, and even control robots. But JavaScript got its start in the browser way back in 1995.</p>
            <hr>
            <p>Things to Learn</p>
            <ul>
                <li>Item One: <input type="text"></li>
                <li>Item Two: <input type="text"></li>
                <li>Item Three: <input type="text"></li>
                <li>Item Four: <input type="text"></li>
            </ul>
            <button>Save</button>
        </section>
        <script src="app.js"></script>
    </body>
</html>
app.js 
let section = document.getElementsByTagName('section')[0];

section.addEventListener('click', (e) => {
  e.target.style.backgroundColor = 'rgb(255, 255, 0)';
});

2 Answers

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

It doesn't look like you've written any code yet.

You'll need to add some code to app.js so that only the INPUT elements are given the new color attribute.

At least give it a good-faith attempt and then ask for help if you have trouble, and be sure to show your code.

Vic Mercier
Vic Mercier
3,276 Points
Vic Mercier
Vic Mercier
3,276 Points

Sorry about my unclear question and thanks for you answer but my question was not in link about this exercise.That means you can remove the files(index.html, app.js).I meant that I would like to know what is the difference between event bubbling and delegation .Please explain me what is delegation.

Thank you very much for your help !You have helped me often and your answers are good???

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

See if this helps make it clear:

Event propagation, or "bubbling" is when an event triggers not only a listener on the element where the event occurred, but also any listeners on parents of that element, all the way up to the "root" (the html element).

Delegation is when you use an event handler on a parent (or higher ancestor) to respond to an event instead of using one on the element itself. Delegation is possible only because of the "bubbling" of the events.

Advantages of using delegation is that one handler can deal with events from several child/descendant elements, and also new elements that are created later will be covered by the same event handler.

Vic Mercier
Vic Mercier
3,276 Points
Vic Mercier
Vic Mercier
3,276 Points

What is an évent handler?

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

The function that runs when an event occurs is called an "event handler". It's the one you pass as the second argument to addEventListener.