waitForElementTransition()

Let's say you have the problem (that many of us have) where you need to wait for the completion of your element's CSS transition before your code continues. You can use this library and call a waitForElementTransition method to wait until the element finishes its css transition before doing other things in your javascript code.

Benefits

Easily wait for an element's css transition to end using JavaScript
Allows you to keep your transition/animation css properties separate from your JS
Native javascript with no dependencies
Safer and more reliable than transitionstart and transitionend events
Plays nicely with the latest specifications

Installation

You can either use the dist file directly in your project:

<script
    type="text/javascript"
    src="/dist/wait-for-element-transition.min.js"
></script>

Or install via npm

npm i wait-for-element-transition

and import

import waitForElementTransition from 'wait-for-element-transition';

Usage

Here's an example where we want to wait for an element's background color to change from black to red.

<style>
    div {
        background-color: black;
        transition-property: background-color;
        transition-duration: 100ms;
        transition-timing-function: ease-out;
    }

    .red {
        background-color: red;
    }
</style>

<div>Transition this element</div>

<script
    type="text/javascript"
    src="/dist/wait-for-element-transition.min.js"
></script>
<script>
    const element = document.querySelector('div');
    element.classList.add('red'); // start transition
    waitForElementTransition(element).then(() => {
        // 100 milliseconds later...
        console.log('element background color changed to red!');
    });
</script>

If the element has already transitioned before the waitForElementTransition() is called, the waitForElementTransition()s promise will resolve immediately. So you can always guarantee that your code will run, just as it would synchronously.

Alternatives

The `transitionend` event

Using the transitionend or animationend events on an Element will allow you to wait until an Element's transition has ended, but this approach is limited:

The events don't fire in the case where a transition is removed before completion (i.e. display is set to "none" or if the css property is removed) and
The events don't fire when there are no css transition properties specified, which doesn't allow us to run the same animation-completion logic on elements which may or may not be animated.

Web Animations API

If done in a supported browser, the same thing in this package can be achieved using the Web Animations API. But consumers of this package may want a less-complex approach.

Development

Watch source files while developing:

npm start

Run test

npm test

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