As somebody who (unfortunately) learned more of jQuery
than raw javascript
I am just now taking the time to replace all of my code with raw javascript
. No, it's not needed, but it's an easier way for me to learn. A problem I am facing is converting all of my $(document).on
with raw javascript
. My website is a "single-page application" and most of my actual HTML
is in different files which are called via Ajax
requests. So, my question is, how would I look for an event
fired from dynamically loaded content? I am assuming I would have to add an onclick
event to them, but how is it that jQuery
does it without needing an onclick
event
?
In jQuery, you can listen to events for dynamically added elements using the on() function. The equivalent in JavaScript is addEventListener() function.
The $() function The dollar function, $(), can be used as shorthand for the getElementById function. To refer to an element in the Document Object Model (DOM) of an HTML page, the usual function identifying an element is: document.
Then came jQuery, a library of tools created by developers around the world, using Javascript. In simple words, jQuery is a lightweight and easy to use JavaScript library that helps in creating complex functionalities with few lines of coding.
A progressive JavaScript framework, Vue. js is considered a good alternative to jQuery. It is an open-source, MVVM, front-end JS framework that is considered ideal to create user interfaces and single-page apps. It is also considered good for web interfaces, desktop, and mobile app development.
Binding handlers in native API is done using addEventListener()
.
To emulate jQuery's event delegation, you could fairly easily create a system that uses the .matches()
method to test the selector you give.
function delegate(el, evt, sel, handler) { el.addEventListener(evt, function(event) { var t = event.target; while (t && t !== this) { if (t.matches(sel)) { handler.call(t, event); } t = t.parentNode; } }); }
There are probably some tweaks to be made, but basically it's a function that takes the element to bind to, like document
, the event type, a selector and the handler.
It starts on the e.target
and traverses up the parents until it gets to the bound element. Each time, it checks to see if the current element matches the selector, and if so, it invokes the handler.
So you'd call it like this:
delegate(document, "click", ".some_elem", function(event) { this.style.border = "2px dashed orange"; });
Here's a live demo that also adds dynamic elements to show that new elements are picked up as well.
function delegate(el, evt, sel, handler) { el.addEventListener(evt, function(event) { var t = event.target; while (t && t !== this) { if (t.matches(sel)) { handler.call(t, event); } t = t.parentNode; } }); } delegate(document, "click", ".some_elem", function(event) { this.parentNode.appendChild(this.cloneNode(true)); this.style.border = "2px dashed orange"; });
<div> <p class="some_elem"> <span> CLICK ME </span> </p> </div>
Here's a shim to add a bit more support for .matches()
.
if (!Element.prototype.matches) { Element.prototype.matches = Element.prototype.matchesSelector || Element.prototype.webkitMatchesSelector || Element.prototype.mozMatchesSelector || Element.prototype.msMatchesSelector || Element.prototype.oMatchesSelector || function(s) { var matches = (this.document || this.ownerDocument).querySelectorAll(s), i = matches.length; while (--i >= 0 && matches.item(i) !== this) {} return i > -1; }; }
Here is a javascript equivalent to on()
jQuery
$(document).on('click', '#my-id', callback); function callback(){ ...handler code here }
Javascript
document.addEventListener('click', function(event) { if (event.target.id == 'my-id') { callback(); } }); function callback(){ ...handler code here }
With this approach, the idea is to make use of event.target. Of course, as the selector changes, your code will have to get more involved
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