How can you create animations in HTML5 without blocking the main thread?

1 Use CSS transitions and animations

One of the easiest ways to create animations in HTML5 is to use CSS transitions and animations, which are supported by most browsers and can be controlled by JavaScript. CSS transitions and animations allow you to change the properties of an element over time, such as its position, size, color, opacity, transform, and filter. CSS transitions and animations are handled by the browser's compositor thread, which is separate from the main thread and can take advantage of the GPU for rendering. This means that they do not block the main thread and have minimal impact on the page performance. However, CSS transitions and animations have some limitations, such as the lack of support for complex paths, physics-based effects, and synchronization with other elements.

2 Use requestAnimationFrame

Another way to create animations in HTML5 is to use requestAnimationFrame, which is a JavaScript method that tells the browser to run a callback function before the next repaint. requestAnimationFrame allows you to create animations that are synchronized with the browser's refresh rate, which is typically 60 frames per second. This ensures that your animations are smooth and consistent, and avoid jank and flicker. requestAnimationFrame also helps to optimize the page performance, as it pauses the animation when the tab is not visible or the device is in low-power mode. However, requestAnimationFrame still runs on the main thread, so you have to be careful not to overload it with too much computation or DOM manipulation.

3 Use Web Workers

A more advanced way to create animations in HTML5 is to use Web Workers, which are a way to run JavaScript code in a background thread, without affecting the main thread. Web Workers can perform complex calculations, fetch data, or manipulate images and audio without blocking the user interface or the animation. Web Workers can communicate with the main thread using messages, which can be simple data or transferable objects. Transferable objects are a way to transfer large data without copying or cloning, which can improve the performance and memory usage. However, Web Workers have some drawbacks, such as the lack of access to the DOM, the window object, and some APIs.

4 Use Web Animations API

A newer way to create animations in HTML5 is to use Web Animations API, which is a JavaScript API that provides a common interface for creating and manipulating animations. Web Animations API allows you to create animations that are similar to CSS transitions and animations, but with more features and flexibility. For example, you can create animations that follow complex paths, have timing functions, have playback controls, and have events and callbacks. Web Animations API also allows you to create animations that are compatible with CSS transitions and animations, and can be manipulated by JavaScript. Web Animations API is designed to be performant and efficient, as it can run on the compositor thread or the main thread, depending on the animation properties and the browser support. However, Web Animations API is still experimental and not widely supported by all browsers.

5 Use Canvas and WebGL

A final way to create animations in HTML5 is to use Canvas and WebGL, which are two ways to draw graphics on the web. Canvas is a HTML element that allows you to draw 2D graphics using JavaScript, while WebGL is a JavaScript API that allows you to draw 3D graphics using the GPU. Canvas and WebGL can create animations that are rich and complex, such as games, simulations, and visualizations. Canvas and WebGL can also use requestAnimationFrame to synchronize with the browser's refresh rate and optimize the performance. However, Canvas and WebGL can be challenging and time-consuming to use, as they require a lot of code, logic, and math. Canvas and WebGL also have some compatibility and security issues, as they depend on the browser and the device capabilities.

6 Here’s what else to consider

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