How to Change the Class Name of a Specific Div on State Change in ReactJS

In ReactJS, dynamically altering the class name of a specific <div> based on state changes is a common requirement for building interactive and responsive user interfaces. Leveraging React’s powerful state management capabilities, you can achieve this functionality efficiently. This guide illustrates how to achieve this functionality efficiently, enhancing the responsiveness and interactivity of your React applications.

To begin, ensure you have a solid understanding of React’s state management and component lifecycle. Then, within your React component, define the state variable that dictates the class name dynamically. Utilize the useState hook to declare and manage the state.

Understanding the Need:

When developing React applications, there’s often a need to dynamically alter the appearance or behavior of certain elements based on changes in application state. One frequent requirement is to change the class name of a specific <div> element dynamically.

Creating the Issue:

To understand the issue, consider a scenario where you want to toggle the appearance of a <div> element based on a button click. Initially, the <div> may have a certain class name, but upon clicking the button, you want to change its class name to reflect a different appearance or behavior.

import React, { useState } from 'react';

const MyComponent = () => {
  const [isActive, setIsActive] = useState(false);

  return (
    <div className={isActive ? 'active' : 'inactive'}>
      {/* Your content here */}
      <button onClick={() => setIsActive(!isActive)}>Toggle Class</button>
    </div>
  );
};

export default MyComponent;

Root Cause:

The issue arises because React’s virtual DOM doesn’t automatically update class names based on state changes. Instead, it re-renders the entire component, potentially causing performance overheads, especially in larger applications.

Solution 1: Using Conditional Rendering:

One approach to address this issue is by using conditional rendering to render different elements based on state. By conditionally rendering different <div> elements with distinct class names, you can achieve the desired behavior.

return (
  {isActive ? (
    <div className="active">
      {/* Active content */}
    </div>
  ) : (
    <div className="inactive">
      {/* Inactive content */}
    </div>
  )}
);

Solution 2: Using className Prop Directly:

Alternatively, you can directly manipulate the className prop of the <div> element based on state changes. This approach provides a straightforward solution without the need for conditional rendering.

return (
  <div className={isActive ? 'active' : 'inactive'}>
    {/* Your content here */}
  </div>
);

Solution 3: Using CSS-in-JS Libraries:

Integrating CSS-in-JS libraries like styled-components or Emotion enables you to define dynamic styles directly within your React components. By defining styles based on state variables, you can effectively change the appearance of specific elements, including <div> elements, in response to state changes.

import styled from 'styled-components';

const StyledDiv = styled.div`
  background-color: ${props => props.isActive ? 'green' : 'red'};
`;

const MyComponent = () => {
  const [isActive, setIsActive] = useState(false);

  return (
    <StyledDiv isActive={isActive}>
      {/* Your content here */}
      <button onClick={() => setIsActive(!isActive)}>Toggle Class</button>
    </StyledDiv>
  );
};

Solution 4: Using Class Names Library:

Leveraging class names libraries like classnames simplifies conditionally applying class names to elements. These libraries provide utility functions to conditionally concatenate class names based on state or other conditions, streamlining your code and improving readability.

import classNames from 'classnames';

const MyComponent = () => {
  const [isActive, setIsActive] = useState(false);

  return (
    <div className={classNames('box', { 'active': isActive, 'inactive': !isActive })}>
      {/* Your content here */}
      <button onClick={() => setIsActive(!isActive)}>Toggle Class</button>
    </div>
  );
};

Solution 5: Using useRef Hook for Direct DOM Manipulation:

Although discouraged in most cases, you can utilize the useRef hook to directly manipulate the DOM element’s class name. However, this approach bypasses React’s virtual DOM reconciliation, potentially leading to unexpected behavior and should be used sparingly.

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

const MyComponent = () => {
  const [isActive, setIsActive] = useState(false);
  const divRef = useRef(null);

  const toggleClass = () => {
    divRef.current.classList.toggle('active');
  };

  return (
    <div ref={divRef} className="box">
      {/* Your content here */}
      <button onClick={toggleClass}>Toggle Class</button>
    </div>
  );
};

These solutions offer various approaches to dynamically change the class name of a specific <div> element based on state changes in ReactJS, catering to different project requirements and development preferences. Experiment with each method to determine the most suitable approach for your application.