31. In React.js, are component props changeable (mutable) or unchangeable (immutable)? Explain why with supporting reasons.
hard

Props in React are used to pass data from a parent component to its child components. They help customize the behavior and appearance of components while maintaining a unidirectional data flow.


Props are immutable in React

In React, props are immutable by default. This means that once props are passed to a child component, they cannot be modified directly within that child component.

  • Immutable objects: When an object is passed as a prop, React treats it as immutable. Any attempt to change its properties within the child component will result in an error.
  • Read-only access: Child components have read-only access to props, ensuring they do not unintentionally alter the data provided by the parent component.

Why Immutable Props are Beneficial

Immutability of props brings multiple advantages to your application:

  1. Predictability and stability: Components behave more predictably since their inputs (props) remain constant throughout the render cycle.
  2. Improved security: Props cannot be tampered with, making your component interactions more secure.
  3. Easier debugging and maintenance: Immutable props reduce the complexity of debugging since state changes are easier to trace.

Example: Immutable Props in Action

import React, { useState } from 'react';

const ParentComponent = () => {
  const [count, setCount] = useState({ count: 0 });

  return (
    <div>
      <ChildComponent {...count} />
      <button onClick={() => setCount({ count: 10 })}>Update Count</button>
    </div>
  );
};

const ChildComponent = ({ count }) => {
  // Attempting to modify the props directly will result in an error
  // const updatedCount = { count: count + 1 };

  return <p>Count: {count.count}</p>;
};

In this example:

  • The ParentComponent maintains the count in its state.
  • It passes the current count to the ChildComponent as props.
  • Attempting to mutate the count prop within the child will cause an error since props are read-only.

Conclusion

React enforces immutability of props to promote a predictable and stable architecture. If you need to update the data passed to a component, the appropriate way is to modify the parent’s state and re-render the child with new props.

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