tween.js

JavaScript (TypeScript) tweening engine for easy animations, incorporating optimised Robert Penner's equations.

[![NPM Version][npm-image]][npm-url] [![CDNJS][cdnjs-image]][cdnjs-url] [![NPM Downloads][downloads-image]][downloads-url] [![Build and Tests][ci-image]][ci-url]

More languages: English, 简体中文

---

<div id="box"></div>

<style>
	#box {
		background-color: deeppink;
		width: 100px;
		height: 100px;
	}
</style>

<script type="module">
	import {Tween, Easing} from 'https://unpkg.com/@tweenjs/tween.js@23.1.3/dist/tween.esm.js'

	const box = document.getElementById('box') // Get the element we want to animate.

	const coords = {x: 0, y: 0} // Start at (0, 0)

	const tween = new Tween(coords, false) // Create a new tween that modifies 'coords'.
		.to({x: 300, y: 200}, 1000) // Move to (300, 200) in 1 second.
		.easing(Easing.Quadratic.InOut) // Use an easing function to make the animation smooth.
		.onUpdate(() => {
			// Called after tween.js updates 'coords'.
			// Move 'box' to the position described by 'coords' with a CSS translation.
			box.style.setProperty('transform', 'translate(' + coords.x + 'px, ' + coords.y + 'px)')
		})
		.start() // Start the tween immediately.

	// Setup the animation loop.
	function animate(time) {
		tween.update(time)
		requestAnimationFrame(animate)
	}
	requestAnimationFrame(animate)
</script>

Try this example on CodePen

Features

• Does one thing only and does it well: tweens properties of an object
• Doesn't take care of CSS units (e.g. appending px)
• Doesn't interpolate colors
• Easing functions are reusable outside of Tween
• Can also use custom easing functions
• Doesn't make its own animation loop, making it flexible for integration into any animation loop.

Examples

Installation

The recommended method is to use import syntax. Here we've listed various install methods starting roughly with the most recommended first and least desirable last. Evaluate all of the following methods to pick what is most suitable for your project.

With npm install and import from node_modules

You can add tween.js as an npm dependency:

npm install @tweenjs/tween.js

Without a build tool

Installed locally

You can import from node_modules if you serve node_modules as part of your website, using a standard importmap script tag. First, assuming node_modules is at the root of your website, you can write an import map like so in your HTML file:

<script type="importmap">
	{
		"imports": {
			"@tweenjs/tween.js": "/node_modules/@tweenjs/tween.js/dist/tween.esm.js"
		}
	}
</script>

Now in any of your module scripts you can import Tween.js by its package name:

<script type="module">
	import {Tween} from '@tweenjs/tween.js'
</script>

Import from CDN

Note that, without the importmap, you can import directly from a CDN as with the first example above, like so:

<script type="module">
	import {Tween} from 'https://unpkg.com/browse/@tweenjs/tween.js@23.1.3/dist/tween.esm.js'
</script>

You can also link your importmap to the CDN instead of a local node_modules folder, if you prefer that:

<script type="importmap">
	{
		"imports": {
			"@tweenjs/tween.js": "https://unpkg.com/browse/@tweenjs/tween.js@23.1.3/dist/tween.esm.js"
		}
	}
</script>

<script type="module">
	import {Tween} from '@tweenjs/tween.js'
</script>

With a build tool

If you are using Node.js, Parcel, Webpack, Rollup, Vite, or another build tool, then you can install @tweenjs/tween.js with npm install @tweenjs/tween.js, and import the library into your JavaScript (or TypeScript) file, and the build tool will know how to find the source code from node_modules without needing to create an importmap script:

import * as TWEEN from '@tweenjs/tween.js'

However, note that this approach requires always running a build tool for your app to work, while the importmap approach will simply work without any build tools as a simple static HTML site.

Manual build

Another approach is to download the source code with git, manually build the library, then place the output in your project. Node.js is required for this.

git clone https://github.com/tweenjs/tween.js
cd tween.js
npm install
npm run build

This will create some builds in the dist directory. There are currently two different builds of the library:

• ES6 Module in /dist/tween.esm.js (recommended)
• UMD in /dist/tween.umd.js (deprecated, will be removed in a future major version)

You are now able to copy one of those two files into your project, and use like this (recommended):

<script type="module">
	import {Tween} from 'path/to/tween.esm.js'
</script>

or (deprecated, to be removed in future major):

<script src="path/to/tween.umd.js"></script>
<script>
	const {Tween} = TWEEN
</script>

where path/to is replaced with the location where you placed the file.

[!Note] You can also download these files from unpkg, for example here: https://unpkg.com/browse/@tweenjs/tween.js@23.1.3/dist/

Global variable from CD