The Web Animations API is a browser-native JavaScript animation control interface. 1. It allows developers to define keyframes and animation options through code to achieve dynamic and interactive animation effects; 2. Use the animate() method to create animations, and can achieve fine controls such as playback, pause, and acceleration through the returned Animation object; 3. Advantages include not relying on CSS or third-party libraries, supporting real-time response to user behavior, compatibility with modern browsers, but paying attention to the limitations of IE and Safari; 4. When using it, you should pay attention to performance optimization, avoid animation overlay, and implement animation callbacks through event monitoring.

The Web Animations API is a powerful but often underestimated tool in modern front-end development. It allows you to directly control animations with JavaScript without relying on CSS or third-party libraries. If you want to achieve more flexible and programmable animations in your web pages, the Web Animations API is a worthwhile choice.

What is the Web Animations API?

Simply put, it is a set of JavaScript interfaces natively supported by the browser for creating and controlling animations. You can use it to define keyframes, set animation duration, loop behavior, etc., all of which can be precisely controlled by code.

Compared with CSS animation, its advantage is that it can dynamically change animation properties, such as responding to user interactions or data changes in real time. It does not require writing keyframes in advance like CSS, nor does it have limited functionality like jQuery's animate method.

How to create a basic animation?

Creating an animation using the Web Animations API usually consists of two parts: defining keyframes and setting timing options.

 const element = document.querySelector('.box');

const keyframes = [
  { transform: 'scale(1)', opacity: 1 },
  { transform: 'scale(1.5)', opacity: 0.5 },
  { transform: 'scale(1)', opacity: 1 }
];

const timingOptions = {
  duration: 1000,
  Iterations: Infinity
};

element.animate(keyframes, timingOptions);

The above code will make an element constantly zoom in and out, achieving a simple breathing lamp effect. in:

• keyframes define the state of each stage of the animation
• timingOptions controls the animation duration, whether it loops, etc.
• animate() is a method on Element to start animation

What makes this method more flexible than CSS animation is that you can modify these parameters at any time, and even dynamically generate new animations based on user operations.

Advanced animation control skills

Although animate() can quickly start animations, if you want to control the playback status more carefully, such as pausing, restoring, or adjusting the playback speed, you need to use the returned Animation object.

 const animation = element.animate(keyframes, timingOptions);

// Pause animation animation.pause();

// Resuming animation.play();

// Set playback rate (2 times the speed)
animation.playbackRate = 2;

// Reverse animation animation.reverse();

This is very useful in some interactive scenarios, such as:

• Accelerate animation when user hovers
• Pause and jump to a specific frame after clicking the button
• Dynamically adjust the animation progress according to the scroll position

In addition, you can also listen to animation events such as start, end, repeat, etc.:

 animation.onfinish = () => {
  console.log('Animation completed');
};

Notes and compatibility

Although the Web Animations API has been widely supported in modern browsers, there are still some details to note:

• Compatibility handling : IE does not support it, Safari supports it with limited levels. If you need to be compatible with old browsers, it is recommended to add polyfill.
• Performance optimization : Try to avoid frequent calls animate() , especially in scroll events, otherwise the page may be stuttered.
• Animation overlay problem : multiple calls animate() will create multiple animation instances, which may interfere with each other. The previous animation can be cleaned up through animation.cancel() .

In addition, if you are already using CSS animation, you can also obtain all animation objects on the current page for unified management through document.timeline.getAnimations() .

Overall, the Web Animations API provides a clean and powerful way to directly control animations in JavaScript. It is not complicated, but is easily overlooked in actual projects. As long as you master the basic structure and control methods, you can replace traditional CSS animations or third-party libraries in many scenarios, bringing higher flexibility and control.

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