Handling Events for Many Elements | kirupa.com


#21

@TallGlassOfMike That still works. The approach described in this tutorial doesn’t work as well in that case, so maybe you’ll want to assign them individually like that.

Otherwise it would mean a more complicated filter. In using a single event listener, you need to be able to tell that what you clicked was what you wanted to be clicked. This was what if (e.target !== e.currentTarget) { ... } was doing - making sure that clicks that were made on #theDude (e.currentTarget) but not any of the one, two, three, four, or five buttons (e.target) were getting ignored. If the background of #theDude was clicked, for example, then e.target === e.currentTarget would be true.

If you have multiple buttons in different hierarchies, then the single handler would have to be applied to the common parent of those buttons. In a worst case scenario, that would be the body element. But then you would need to check e.target for basically every click made in the entire document to see if it’s one of your buttons. The check for this wouldn’t actually be too hard if you had a list of selectors targeting your buttons. It could be as simple as:

document.body.addEventListener('click', function (e) {
    if (e.target.matches('#parent1 .button, #parent2 .button, #parent3 .button')) {
        // do something with your clicked button
    }
});

But there is the downside of this check happening for every click in the common parent. If you’re ok with that (does one if check really matter that much?) then this could work for you. One event handler is a lot easier to manage than multiple event handlers and it means the dom can be changed and have .button elements added and removed and re-added without affecting the click handler at all.


#22

Excellent post, thanks! How would this be done for contenteditable div tags? It looks like this:

<div id="theParent" contenteditable="true"></div>
    <div class="el"...></div>
    <div class="el"...></div>
    ...

With JavaScript:

var e = document.querySelector("#theParent");
e.addEventListener("input", doSomething, false);

When I run this, it returns e.target as “theParent”. I tried adding contenteditable to each of the inner div tags as well, which didn’t work. Would greatly appreciate any help!


#23

If you replace the input event with click, then the appropriate element you clicked on works - even if the parent is a contenteditable div element:

<body>
  <div id="theParent" contenteditable="true">
    <div id="foo" class="el">A</div>
    <div id="bar" class="el">B</div>
  </div>

  <script>
    var theParent = document.querySelector("#theParent");
    theParent.addEventListener("click", doSomething, false);

    function doSomething(e) {
      if (e.target !== e.currentTarget) {
          var clickedItem = e.target.id;
          console.log("Hello " + clickedItem);
      }
      e.stopPropagation();
    }
  </script>

The input event is a bit bizarre in how it behaves. Can you share more on what you are trying to do?

Thanks,
Kirupa :nerd_face:


#24

Thanks for the suggestion, although click won’t work for this use case. I’m adding paragraphs within a larger text window. Each paragraph is within a div tag, and the entire text window is inside the parent div. Every time the user enters new text, the event listener fires only on the specific div paragraph


#25

Can you provide a link to your page or a smaller repro? This seems like a very reasonable scenario, so there has to be some magical approach that works. I’d love to fiddle with it for a bit :stuck_out_tongue:


#26

I am making a calculator pls how can i apply this to mine?Your explanation was legit but i learn slow

2018-05-26_21h22_04


#27

Can you be a bit more specific in what you’d like help with? :slight_smile:


#28

Yes sure. Sorry I was very frustrate at the time I sent my last message. A building a calculator and aim is quite simple. I want this to have keys from 1-9 including 0 of course. So when clicked, that is any of the buttons like 3 it display in a screen (a div with light background) so as my of picture shows i have gotten the keys in a variable with a query selector. So should I add an event listener one by one on each element or is there an easier way.


#29

You can add an event listener to the parent of the keys like the article describes. Then you can then check for which key triggered the event. That would be the cleaner way to do it :slight_smile: