How can you measure and optimize front-end performance with the React Profiler?

1 What is the React Profiler?

The React Profiler is a component that you can wrap around any part of your app that you want to measure the performance of. It collects information about how often the components render, how long they take to render, and what causes them to re-render. The Profiler can be used in both development and production modes, but it has more features and details in development mode. To use the Profiler, you need to install the React DevTools extension for your browser, which will show you a tab called Profiler where you can see the results of your measurements.

2 How to measure rendering time with the React Profiler?

Rendering time is the time it takes for a component to generate its output, which can be either HTML elements or other components. Rendering time can be affected by many factors, such as the complexity of the component, the size of its props and state, and the number of children it has. To measure the rendering time of your components with the React Profiler, you need to wrap them with a <Profiler> tag and provide an id and an onRender callback function. The onRender function will receive an object with various metrics, such as actualDuration, which is the time spent rendering the component and its descendants for the current update. You can use this function to log, store, or display the metrics as you wish.

3 How to measure commit phase duration with the React Profiler?

Commit phase duration is the time it takes for React to apply the changes from the render phase to the DOM. Commit phase duration can be affected by the number and type of DOM mutations, the use of lifecycles or effects, and the browser's layout and paint processes. To measure the commit phase duration of your components with the React Profiler, you need to use the same <Profiler> tag and onRender function as before, but this time look for the metric called phase, which will tell you if the current update is in the render or commit phase. You can also use the metric called commitTime, which is the timestamp when React committed the current update.

4 How to measure effect duration with the React Profiler?

Effect duration is the time it takes for React to run the effects of a component after it has been committed to the DOM. Effects are functions that you can use to perform side effects, such as fetching data, updating state, or subscribing to events. Effect duration can be affected by the complexity and frequency of the effects, the dependencies of the effects, and the availability of the resources they need. To measure the effect duration of your components with the React Profiler, you need to use the same <Profiler> tag and onRender function as before, but this time look for the metric called interactions, which is an array of objects that describe the effects that were run for the current update. Each object has a name, a timestamp, and an id. You can use these objects to track the start and end time of each effect and calculate their duration.

5 How to optimize rendering time with the React Profiler?

One of the most common ways to optimize rendering time is to prevent unnecessary re-renders of your components. To do this, you need to identify the components that re-render too often or too slowly, and the causes of their re-renders. You can use the React Profiler to see the number of renders and the rendering time of each component, and to filter them by the type of update (props, state, context, or force update). You can also use the React Profiler to see the props and state of each component, and to compare them between renders to see what changed. To prevent unnecessary re-renders, you can use techniques such as memoizing components, using useCallback and useMemo hooks, and avoiding inline functions and objects as props.

6 How to optimize commit phase duration with the React Profiler?

One of the most common ways to optimize commit phase duration is to reduce the amount of DOM mutations that your components cause. To do this, you need to identify the components that cause too many or too slow DOM mutations, and the reasons for them. You can use the React Profiler to see the number of DOM nodes and the commit time of each component, and to filter them by the type of effect (layout or passive). You can also use the React Profiler to see the DOM tree of your app, and to highlight the components that updated in the last commit. To reduce DOM mutations, you can use techniques such as using keys for lists, avoiding unnecessary elements or wrappers, and using CSS transitions or animations instead of JavaScript.

7 Here’s what else to consider

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