Understanding 'Props' in React

In the world of React, a 'prop' is an integral concept. 'Props' is short for properties, and these are essentially read-only attributes that are used within a component. To break this down, let's explore this concept with a bit more depth.

React is designed to be highly modular, with individual components that can be reused and combined in a variety of ways. These components can often take different types of information or configurations to control their behavior.

This is where 'props' come in. When you're creating a React component, you can specify props – much like HTML attributes – to control how that component behaves. The key trait of props, however, is that they are read-only. This means that a component can only read the props given to it but cannot change its value directly.

function Welcome(props) {
  return <h1>Hello, {props.name}</h1>;
}

const element = <Welcome name="Sara" />;
ReactDOM.render(
  element,
  document.getElementById('root')
);

In the example above, we define a Welcome component that accepts a prop called 'name'. We then use this 'name' prop in the returned JSX (which is the component's output).

By keeping props read-only, React ensures one-way data flow, which can make applications easier to understand and predict. This is part of the philosophy of "immutable data" in React.

It's important to understand that each component should be pure – it should not modify its input, and for the same input, it should always return the same output. This is why React props must always stay read-only.

In conclusion, 'props' in React are used for passing data from one component to another, as parameters from function to another. They are the critical link between React components, promoting reusability, modularity, and readability. Understanding and effectively using 'props' is crucial in mastering React.