Reactjs - `component` vs `render` in Route

Question

I have two doubts regarding usage of Route from react-router-dom(v4.3.1):

1. When do we use component v

Answer 1

When you pass a component to the component prop, the component will get the path parameters in the props.match.params object, i.e props.match.params.username in your example:

class ProfileComponent extends React.Component {
  render() {
    return <div>{this.props.match.params.username}</div>;
  }
}

When using the render prop, the path parameters can be accessed through the props given to the render function:

<Route
  exact
  path='/u/:username/'
  render={(props) => 
    <ProfileComponent username={props.match.params.username}/>
  }
/>

You generally use the render prop when you need some data from the component that contains your routes, since the component prop gives no real way of passing in additional props to the component.