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Parent-Child Relationship in Component Composition (Live Playground)

Component composition is an essential aspect of building modular and reusable components in React. The parent-child relationship is the cornerstone of this approach. In this tutorial, we'll explore the parent-child relationship with sample code and simple explanations.

Creating Parent and Child Components​

To demonstrate the parent-child relationship, let's create two components: a Parent component and a Child component.

JavaScript
import React from 'react';

function Parent() {
  return (
    <div>
      <h1>I am the Parent Component</h1>
      <Child />
    </div>
  );
}

function Child() {
  return <p>I am the Child Component</p>;
}

export default Parent;

In this example, the Child component is rendered inside the Parent component, establishing a parent-child relationship.

Live Playground, Try it Yourself

Passing Data from Parent to Child​

One of the main advantages of the parent-child relationship is the ability to pass data from the parent component to the child component using props.

JavaScript
import React from 'react';

function Parent() {
  const message = 'Hello from Parent';

  return (
    <div>
      <h1>I am the Parent Component</h1>
      <Child text={message} />
    </div>
  );
}

function Child(props) {
  return <p>{props.text}</p>;
}

export default Parent;

In this example, we pass the message variable from the Parent component to the Child component using the text prop.

Live Playground, Try it Yourself

Callback Functions for Child-to-Parent Communication​

To communicate from the child component to the parent component, you can pass a callback function as a prop.

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

function Parent() {
  const [message, setMessage] = useState('No message received.');

  const handleMessage = text => {
    setMessage(`Message from Child: ${text}`);
  };

  return (
    <div>
      <h1>I am the Parent Component</h1>
      <p>{message}</p>
      <Child onSendMessage={handleMessage} />
    </div>
  );
}

function Child(props) {
  const handleClick = () => {
    props.onSendMessage('Hello from Child');
  };

  return <button onClick={handleClick}>Send Message</button>;
}

export default Parent;

In this example, we pass the handleMessage function from the Parent component to the Child component using the onSendMessage prop. The Child component can then call this function to communicate with the Parent.

Live Playground, Try it Yourself

Conclusion​

Understanding the parent-child relationship in React component composition is crucial for creating modular and reusable components. By creating parent and child components, passing data from parent to child using props, and using callback functions for child-to-parent communication, you can build more maintainable and scalable applications.