The React useEffect hook is a robust device within the React developer’s arsenal. It means that you can carry out unwanted effects in your useful parts, equivalent to information fetching, subscriptions, or manually altering the DOM. This text goals to offer a complete understanding of the useEffect hook, its utilization, and finest practices.

Desk of Contents

What’s React useEffect?

The useEffect hook is a operate offered by React that means that you can deal with unwanted effects in your useful parts. Unwanted side effects are any operations that don’t contain the rendering of parts, equivalent to API calls, timers, occasion listeners, and extra.

Before hooks were introduced in React 16.8, unwanted effects have been dealt with in lifecycle strategies at school parts. However with the introduction of hooks, now you can use unwanted effects in your useful parts with the useEffect hook.

Primary syntax of useEffect

The useEffect hook takes two arguments: a operate the place you outline your aspect impact and a dependency array. The operate runs after each render, together with the primary one, until you specify a dependency array.

The dependency array is a solution to inform React when to run your impact. Should you move an empty array ([]), the impact will solely run as soon as after the primary render. Should you move variables within the array, the impact will run each time these variables change.

Learn how to Use React useEffect

Utilizing the useEffect hook is easy. You name useEffect and move a operate to it. This operate incorporates your aspect impact. Let’s have a look at an instance:

useEffect(() => {

On this instance, we’re altering the doc’s title. It is a aspect impact, and we’re utilizing useEffect to carry out it.

Utilizing the dependency array

The dependency array is a robust characteristic of useEffect. It means that you can management when your impact runs. Right here’s an instance:

const [count, setCount] = useState(0);

useEffect(() => {
  doc.title = `You clicked ${depend} occasions`;
}, [count]);

On this instance, the impact runs each time the depend state modifications as a result of we’ve included depend within the dependency array.

Frequent Use Instances for useEffect

There are numerous use instances for the useEffect hook. Listed here are just a few frequent ones.

Information fetching

Probably the most frequent use instances for useEffect is information fetching. You should use useEffect to fetch information from an API and replace your element’s state with the fetched information.

Occasion listeners

You should use useEffect so as to add occasion listeners to your element. That is helpful for dealing with person interactions, equivalent to clicks or key presses.


useEffect can be helpful for organising timers, equivalent to setTimeout or setInterval. You should use it to carry out an motion after a sure period of time has handed.

Finest Practices for Utilizing useEffect

Whereas useEffect is a robust device, it’s vital to make use of it appropriately to keep away from potential points. Listed here are some finest practices to bear in mind.

Clear up your results

Some results needs to be cleaned up earlier than the element is unmounted to keep away from reminiscence leaks. That is very true for results that create subscriptions or occasion listeners. To wash up an impact, you may return a operate out of your impact that performs the cleanup.

Use a number of results to separate considerations

If in case you have a number of unrelated unwanted effects, it’s a great observe to make use of a number of useEffect calls to separate considerations. This makes your code simpler to grasp and take a look at.

Don’t overlook the dependency array

The dependency array is a vital a part of useEffect. Forgetting to incorporate it could possibly result in surprising habits. Make certain to incorporate all of the variables your impact relies on within the array.

In conclusion, the React useEffect hook is a flexible device that means that you can deal with unwanted effects in your useful parts. By understanding its utilization and finest practices, you may write extra environment friendly and maintainable React code.