React useEffect Hook

React useEffect Hook

The React useEffect hook allows you to synchronize a component with an external system, such as a browser API or a web socket connection. It is a powerful tool that can help you manage side effects in your application.

The basic syntax for useEffect is as follows:

useEffect(() => { // code to run on component mount or update }, [dependencies]);

The first argument is a function that contains the code you want to run, and the second argument is an array of dependencies that are used to determine when the effect should be re-run.

For example, let's say you have a component that needs to fetch data from an API when it mounts. You can use useEffect to handle this:

In this example, the effect is only run once on component mount, since the dependency array is empty. However, if you need to re-fetch the data when a prop changes, you can add that prop to the dependency array:

In this example, the effect will re-run whenever the id prop changes, and the API call will be made with the updated id.

It is important to note that useEffect should not be used for anything that can be done in the render function. Also, useEffect is only called after the first render and will not be called again until the next render.

In conclusion, useEffect is a useful tool for managing side effects in React, such as synchronizing with external systems or handling cleanup logic. It can be used to handle any logic that needs to run on component mount or update, and the dependency array can be used to control when the effect should be re-run.