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The Road to React: The One with Hooks

React Props

Explore how to move data from global scope into component state and pass it via props, enabling clear communication between parent and child components. Understand how props prevent global scope pollution and allow data handling across multiple components in React.

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We are currently using the list variable as a global variable in the current application. We used it directly from the global scope in the App component, and again in the List component. This could work if you only had one variable, but it doesn’t scale with multiple variables across multiple components from many different files.

By using props in react, we can pass variables as information from one component to another component. This creates a clear communication channel between parent and child components.

Before using props, we’ll move the list from the global scope into the App component and rename it to its actual domain:

Node.js
const App = () => {
  const stories = [
    {
      title: 'React',
      url: 'https://reactjs.org/',
      author: 'Jordan Walke',
      num_comments: 3,
      points: 4,
      objectID: 0,
    },
    {
      title: 'Redux',
      url: 'https://redux.js.org/',
      author: 'Dan Abramov, Andrew Clark',
      num_comments: 2,
      points: 5,
      objectID: 1,
    },
  ];
  const handleChange = event => { ... };
  return ( ... );
};

Next, we’ll use React props to pass the array to the List component:

Node.js
const App = () => {
  const stories = [ ... ];
  const handleChange = event => { ... };
  return (
    <div>
      <h1>My Hacker Stories</h1>
      <label htmlFor="search">Search: </label>
      <input id="search" type="text" onChange={handleChange} />
      <hr />
      <List list={stories} />
    </div>
  );
};

The variable is called stories in the App component, and we pass it under this name to the List component. In the List component’s instantiation, however, it is assigned to the list attribute. We access it as list from the props object in the List component’s function signature:

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Using this operation, we’ve prevented the list/stories variable from polluting the global scope in the App component. Since stories is not used in the App component directly, but in one of its child components, we passed them as props to the List component. There, we can access it through the first function signature’s argument, called props.

Exercise

Test yourself!

1.

Props are way of passing data from one component to another

A.

True

B.

False

1 / 2