setInterval in React Components Using Hooks
Tags: react, abotwrotethis
Published: 2023-04-20 06:12:02

React components are the building blocks of a React application. Hooks are a new feature introduced in React 16.8 that allows you to use state and other React features without writing a class. In this tutorial, we'll cover how to use the setInterval function in React components using hooks.

## Introduction to setInterval in React Components

The setInterval function is a JavaScript method that allows you to call a function after a specific time interval. It is useful in updating a state in the background without causing the application to freeze. Here's an example of how setInterval works:

```
setInterval(() => {
  console.log('Hello World')
}, 1000)
```

This code will log "Hello World" to the console every second.

## Using setInterval with React Hooks

React provides a useEffect hook that you can use to interact with the DOM or perform side effects. Our goal is to use setInterval to update a state variable in our component without freezing the application. Here's an example:

```javascript
import React, { useState, useEffect } from 'react'

function App() {
  const [count, setCount] = useState(0)

  useEffect(() => {
    const intervalId = setInterval(() => {
      setCount(count => count + 1)
    }, 1000)

    return () => clearInterval(intervalId)
  }, [])

  return (
    <div>
      <p>{count}</p>
    </div>
  )
}

export default App
```

In this example, we define a state variable called "count" and initialize it to 0 using the useState hook. We then use useEffect hook to update the "count" variable with setInterval function. The useEffect hook runs after the component is mounted, and it subscribes to the setInterval function which invokes the Lambda function to update the "count" variable every second.

## How setInterval Works with React Hooks

In React, when a state variable changes, the entire component re-renders. This means the React virtual DOM performs a diff and only updates the necessary parts in the real DOM tree. However, when a setInterval function is used to update the state, it can cause the entire component to re-render every time, which can lead to a poor user experience.

To avoid this issue, we specified an empty array as the second parameter to useEffect hook, telling React to only subscribe to the useEffect hook once, after component mounting. The return function of the useEffect hook function returns another lambda function that will clear the timer interval once the component is no longer in the DOM.

## Setting an Interval with Variable Time

In the previous example, we set the interval time to one second because we wanted to update the count every second. However, what if we wanted to update the count every two seconds or five seconds? Here's how you can define the interval time using an input variable:

```javascript
import React, { useState, useEffect } from 'react'

function App() {
  const [count, setCount] = useState(0)
  const [intervalTime, setIntervalTime] = useState(1000)

  useEffect(() => {
    const intervalId = setInterval(() => {
      setCount(count => count + 1)
    }, intervalTime)

    return () => clearInterval(intervalId)
  }, [intervalTime])

  return (
    <div>
      <p>{count}</p>

      <input
        type="number"
        placeholder="Enter interval time"
        value={intervalTime}
        onChange={e => setIntervalTime(parseInt(e.target.value))}
      />
    </div>
  )
}

export default App
```

In this example, we created a new state variable called "intervalTime" and initialized it to 1000 (1 second). We then added another input field that allows the user to define a custom interval time.

We also updated the useEffect hook to watch for the intervalTime state variable, so that when the interval time is changed, the useEffect hook will clear the timer interval for the old interval time and create a new one for the new interval time.

## Conclusion

setInterval is a useful method in updating the state of a React component without causing the application to freeze. Hooks are a powerful feature of React that allows you to use state and other React features without writing a class. By using the useEffect hook, we can subscribe to the setInterval function in a React component and update the state in the background without causing unnecessary re-renders.

Overall, React Hooks is a powerful and efficient way to develop React applications, and with practice, you can easily build responsive and scalable applications quickly.