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React has become one of the most popular libraries for building user interfaces, offering many hooks to simplify development and improve performance. One of the lesser-understood but extremely useful hooks in React is useRef. While many developers are familiar with hooks like useState and useEffect, useRef tends to be somewhat elusive. In this article, we will dive deep into understanding useRef and how it can be used to access DOM elements in React.

How to Use useEffect Hook for Side Effects

What is useRef in React?

The useRef hook is a part of React’s Hooks API, introduced in React 16.8. It allows you to persist values between renders without causing re-renders. While it’s often used to keep references to DOM elements, it has other uses as well, such as holding mutable values that don’t trigger re-renders when changed.

The basic syntax of useRef

const myRef = useRef(initialValue);

Here, myRef is the reference object returned by useRef, and initialValue is the initial value assigned to the reference. This reference object has a current property, which can hold the DOM element or any mutable value.

const inputRef = useRef(null);

In the example above, inputRef is a reference to a DOM element (in this case, an input element). By passing null as the initial value, you’re ensuring that the reference is initially empty and will be populated when the component mounts.

Why use useRef to access DOM elements?

In React, DOM elements are abstracted away, and you don’t usually interact with them directly. Instead, you manage state, props, and events, letting React take care of the DOM updates. However, there are situations where you might need to interact with the DOM directly, such as focusing an input element, measuring an element’s size, or triggering animations.

Traditionally, this would involve using document.getElementById or document.querySelector in vanilla JavaScript. However, React encourages a declarative approach where you avoid direct DOM manipulation whenever possible. That’s where useRef comes in—it allows you to interact with the DOM without breaking the declarative nature of React.

Advantages of using useRef:

• Avoids re-renders: Unlike state variables, updating a useRef does not cause a re-render of the component, which can improve performance in certain situations.
• Maintains state between renders: It’s useful for persisting values or references across renders without losing them.
• Accessing DOM elements: It’s a clean and easy way to access and interact with DOM elements directly when necessary.

How to use useRef to access DOM elements

To understand how useRef works in practice, let’s walk through an example where we will use useRef to focus an input element when a button is clicked.

Example 1: Focusing an input field

In this example, we will create a simple form with a button that, when clicked, focuses the input field.

import React, { useRef } from 'react';

const FocusInput = () => {
  const inputRef = useRef(null);

  const handleFocus = () => {
    inputRef.current.focus();
  };

  return (
    <div>
      <input ref={inputRef} type="text" placeholder="Click button to focus" />
      <button onClick={handleFocus}>Focus the input</button>
    </div>
  );
};

export default FocusInput;

Explanation:

1. Creating the reference: We declare inputRef using useRef and initialize it with null.
2. Attaching the reference to the input: We assign inputRef to the ref attribute of the <input> element. This gives us a reference to the DOM node.
3. Accessing the DOM: When the button is clicked, the handleFocus function is invoked. Inside this function, we access the input element via inputRef.current and call the focus() method to focus the input.

In this way, useRef allows you to directly access and manipulate DOM elements when necessary.

More Advanced use of useRef

While the example above is relatively simple, useRef can be used for more advanced tasks. Below are some additional use cases for useRef in React.

1. Storing Mutable Values Without Triggering Re-renders

In React, useState causes the component to re-render whenever the state changes. Sometimes, you may want to store a mutable value that doesn’t trigger a re-render. This is where useRef can help.

Example: Tracking Previous Values

Let’s say you want to track the previous value of a state variable without causing unnecessary re-renders.

import React, { useState, useRef, useEffect } from 'react';

const PreviousValue = () => {
  const [count, setCount] = useState(0);
  const prevCountRef = useRef();

  useEffect(() => {
    prevCountRef.current = count;
  }, [count]);

  return (
    <div>
      <h1>Current count: {count}</h1>
      <h2>Previous count: {prevCountRef.current}</h2>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
};

export default PreviousValue;

Explanation:

• useRef is used to store the previous value of the count state variable.
• Every time count changes, the useEffect hook updates the prevCountRef.current with the current count.
• Since useRef does not cause re-renders, this approach avoids unnecessary updates while still maintaining the previous value.

2. Storing Interval or Timeout IDs

Another use case for useRef is storing IDs for setInterval or setTimeout functions, ensuring they persist across renders without triggering re-renders.

import React, { useState, useEffect, useRef } from 'react';

const Timer = () => {
  const [time, setTime] = useState(0);
  const intervalRef = useRef();

  useEffect(() => {
    intervalRef.current = setInterval(() => {
      setTime((prevTime) => prevTime + 1);
    }, 1000);

    return () => {
      clearInterval(intervalRef.current);
    };
  }, []);

  return (
    <div>
      <h1>Time: {time} seconds</h1>
    </div>
  );
};

export default Timer;

Explanation:

• useRef is used to store the interval ID, which ensures that it doesn’t get reset on each render.
• The clearInterval method is called inside the return function of the useEffect hook to clear the interval when the component unmounts.

Conclusion

The useRef hook is a powerful tool in React that allows you to interact with the DOM directly, store mutable values, and persist data between renders without causing unnecessary re-renders. While useState and useEffect are great for handling state and side effects, useRef shines when you need to keep track of DOM elements or mutable values.

Whether you are managing focus on an input field, tracking previous values, or handling timeouts, useRef provides a clean, efficient way to manage those tasks in React.

By understanding and using useRef effectively, you can write more efficient and readable React code while maintaining the declarative and functional approach that React encourages.

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