React - Props

props is the only object argument passed to a component

Props is similar to State, but it is public and not fully controlled by the component.

in React - JSX

<MyComponent name={javascriptVariable} color="Blue"/>

will create two props

• props.name
• and props.color

Props:

• must be named from the component's own point of view rather than the context in which it is being used.
• are read-only. A component must never modify its own props. It must modify it via this.setState() <note important>All React components must act like pure functions with respect to their props.</note> See React - State

Default values are defined by assigning to the special defaultProps property to the component.

• A class greeting component with one prop: name

class Greeting extends React.Component {
  render() {
    return (
      <h1>Hello, {this.props.name}</h1>
    );
  }
}

• Specifies the default value for the name prop:

Greeting.defaultProps = {
  name: 'Stranger (Default)'
};

• And render

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

<div id="root">
<!-- called the "root" DOM node because everything inside it will be managed by React DOM -->
</div>

built-in Type checking in React is known as prop-types

With the chrome plugin

• https://facebook.github.io/react/docs/typechecking-with-proptypes.html