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React Props


Props are arguments passed into React components.

Props are passed to components via HTML attributes.


React Props

React Props are like function arguments in JavaScript and attributes in HTML.

To send props into a component, use the same syntax as HTML attributes:

Example

Add a "brand" attribute to the Car element:

const myelement = <Car brand="Ford" />;

The component receives the argument as a props object:

Example

Use the brand attribute in the component:

class Car extends React.Component {
  render() {
    return <h2>I am a {this.props.brand}!</h2>;
  }
}

Run Example »


Pass Data

Props are also how you pass data from one component to another, as parameters.

Example

Send the "brand" property from the Garage component to the Car component:

class Car extends React.Component {
  render() {
    return <h2>I am a {this.props.brand}!</h2>;
  }
}

class Garage extends React.Component {
  render() {
    return (
      <div>
      <h1>Who lives in my garage?</h1>
      <Car brand="Ford" />
      </div>
    );
  }
}

ReactDOM.render(<Garage />, document.getElementById('root'));

Run Example »

If you have a variable to send, and not a string as in the example above, you just put the variable name inside curly brackets:

Example

Create a variable named "carname" and send it to the Car component:

class Car extends React.Component {
  render() {
    return <h2>I am a {this.props.brand}!</h2>;
  }
}

class Garage extends React.Component {
  render() {
    const carname = "Ford";
    return (
      <div>
      <h1>Who lives in my garage?</h1>
      <Car brand={carname} />
      </div>
    );
  }
}

ReactDOM.render(<Garage />, document.getElementById('root'));

Run Example »

Or if it was an object:

Example

Create an object named "carinfo" and send it to the Car component:

class Car extends React.Component {
  render() {
    return <h2>I am a {this.props.brand.model}!</h2>;
  }
}

class Garage extends React.Component {
  render() {
    const carinfo = {name: "Ford", model: "Mustang"};
    return (
      <div>
      <h1>Who lives in my garage?</h1>
      <Car brand={carinfo} />
      </div>
    );
  }
}

ReactDOM.render(<Garage />, document.getElementById('root'));

Run Example »


Props in the Constructor

If your component has a constructor function, the props should always be passed to the constructor and also to the React.Component via the super() method.

Example

class Car extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    return <h2>I am a {this.props.model}!</h2>;
  }
}

ReactDOM.render(<Car model="Mustang"/>, document.getElementById('root'));

Note: React Props are read-only! You will get an error if you try to change their value.