Animate Plus

Animate Plus is a JavaScript animation library focusing on performance and authoring flexibility. It aims to deliver a steady 60 FPS and weighs less than 2 KB (minified and gzipped), making it particularly well-suited for mobile.

Getting started

npm install animateplus or download animateplus.js and start animating things:

import animate from "/animateplus.js";

animate({
  elements: "div",
  duration: 2000,
  delay: index => index * 100,
  transform: ["scale(0)", "scale(1)"]
})
.then(options => animate({
  ...options,
  transform: ["translate(0%)", "translate(500%)"]
}));

Preview this example →

Options

elements

Default	Type
null	String | Element | NodeList | Array

Determines the DOM elements to animate. You can either pass it a CSS selector or DOM elements.

animate({
  elements: document.body.children,
  transform: ["rotate(0turn)", "rotate(1turn)"]
});

easing

Default	Type
out-elastic	String

Determines the acceleration curve of your animation.

constant	accelerate	decelerate	accelerate-decelerate
linear	in-cubic	out-cubic	in-out-cubic
	in-quartic	out-quartic	in-out-quartic
	in-quintic	out-quintic	in-out-quintic
	in-quintic	out-quintic	in-out-quintic
	in-exponential	out-exponential	in-out-exponential
	in-circular	out-circular	in-out-circular
	in-elastic	out-elastic	in-out-elastic

The amplitude and period of elastic easings can be configured by providing space-separated values. Amplitude defaults to 1, period to 0.4.

// Increase elasticity
animate({
  elements: "span",
  easing: "out-elastic 1.4 0.2",
  transform: ["translate(0px)", "translate(500px)"]
});

duration

Default	Type
1000	Number | Function

Determines the duration of your animation in milliseconds. By passing it a callback, you can define a different duration for each element. The callback takes the index of each element as its argument and returns a number.

// First element fades out in 1s, second element in 2s, etc.
animate({
  elements: "span",
  easing: "linear",
  duration: index => (index + 1) * 1000,
  opacity: [1, 0]
});

delay

Default	Type
0	Number | Function

Determines the delay of your animation in milliseconds. By passing it a callback, you can define a different delay for each element. The callback takes the index of each element as its argument and returns a number.

// First element fades out after 1s, second element after 2s, etc.
animate({
  elements: "span",
  easing: "linear",
  delay: index => (index + 1) * 1000,
  opacity: [1, 0]
});

loop

Default	Type
false	Boolean

Determines if the animation should repeat.

direction

Default	Type
normal	String

Determines the direction of the animation. reverse runs the animation backwards, alternate switches direction after each iteration if the animation loops.

speed

Default	Type
1	Number

Determines the animation playback rate. Useful in the authoring process to speed up some parts of a long sequence (value above 1) or slow down a specific animation to observe it (value below 1).

optimize

Default	Type
false	Boolean

Forces hardware acceleration during an animation if set to true. Unless you experience performance issues, it's recommended to leave it off as hardware acceleration comes with potentially harmful side-effects.

change

Default	Type
null	Function

Defines a callback invoked on every frame of the animation. The callback takes as its argument the animation progress (between 0 and 1) and can be used on its own without being tied to elements.

// Linearly outputs the percentage increase during 5s
animate({
  duration: 5000,
  easing: "linear",
  change: progress =>
    document.body.textContent = `${Math.round(progress * 100)}%`
});

Animations

Animate Plus lets you animate HTML and SVG elements with any property that takes numeric values, including hexadecimal colors.

// Animate the radius and fill color of an SVG circle
animate({
  elements: "circle",
  r: [0, 50],
  fill: ["#80f", "#fc0"]
});

Each property you animate needs an array defining the start and end values. For convenience, you can omit everything but the numbers in the end values.

// Same as ["translate(0px)", "translate(100px)"]
animate({
  elements: "span",
  transform: ["translate(0px)", 100]
});

These arrays can optionally be returned by a callback that takes the index of each element, just like with duration and delay.

// First element translates by 100px, second element by 200px, etc.
animate({
  elements: "span",
  transform: index => ["translate(0px)", (index + 1) * 100]
});

Promise

animate() returns a promise which resolves once the animation finishes. The promise resolves to the object initially passed to animate(), making animation chaining straightforward and convenient. The Getting started section gives you a basic promise example.

Since Animate Plus relies on native promises, you can benefit from all the usual features promises provide, such as Promise.all, Promise.race, and especially async/await which makes animation timelines easy to set up.

const play = async () => {
  const options = await animate({
    elements: "span",
    duration: 3000,
    transform: ["translateY(-100vh)", 0]
  });

  await animate({
    ...options,
    transform: ["rotate(0turn)", 1]
  });

  await animate({
    ...options,
    duration: 800,
    easing: "in-quintic",
    transform: ["scale(1)", 0]
  });
};

play();

Preview this example →

Additional functions

stop

Stops the animations on the elements passed as the argument.

import {stop} from "/animateplus.js";

animate({
  elements: "span",
  easing: "linear",
  duration: index => 8000 + index * 200,
  loop: true,
  transform: ["rotate(0deg)", 360]
});

document.addEventListener("click", ({target}) => stop(target));

Preview this example →

delay

Sets a timer in milliseconds. It differentiates from setTimeout() by returning a promise and being more accurate, consistent and battery-friendly. The delay option relies internally on this method.

import {delay} from "/animateplus.js";

delay(500).then(time => console.log(`${time}ms elapsed`));

Browser support

Animate Plus is provided as a native ES2015 module, which means you may need to transpile it depending on your browser support policy. The library works as is using <script type=module> in the following browsers:

• Chrome 61
• Safari 11.1
• Firefox 57 with dom.moduleScripts.enabled

Best practices

Animations play a major role in the design of good user interfaces. They help connecting actions to consequences, make the flow of interactions manifest, and greatly improve the polish and perception of a product. However, animations can be damaging and detrimental to the user experience if they get in the way. Here are a few best practices to keep your animations effective and enjoyable:

• Speed: Keep your animations fast. A quick animation makes a software feel more productive and responsive. The optimal duration depends on the effect and animation curve, but in most cases you should likely stay under 500 milliseconds.
• Easing: The animation curve contributes greatly to a well-crafted animation. The ease-out options are usually a safe bet as animations kick off promptly, making them react to user interactions instantaneously.
• Performance: Having no animation is better than animations that stutter. When animating HTML elements, aim for using exclusively transform and opacity as these are the only properties browsers can animate cheaply.
• Restraint: Tone down your animations and respect user preferences. Animations can rapidly feel overwhelming and cause motion sickness, so it's important to keep them subtle and to attenuate them even more for users who need reduced motion, for example by using matchMedia("(prefers-reduced-motion)") in JavaScript.

Examples

• Stress test: 500 elements animated concurrently.
• Morphing: CSS polygon morphing using clip-path.
• Motion path: Animation along a custom path.
• Line drawing: SVG line drawing animation.
• Elasticity: SVG circles following your clicks.
• Anchors: Anchor scrolling animation using change().
• Progress: Animation progress using change().
• Text: Text splitting animation.