React is component-based

In React, elements are building blocks of components. The simplest way to define a React component is to define a function:

function Greeter(props) { 
  return <h3>Hello, {props.name}!</h3>; 
}  

However, you can also use ECMAScript 6 class to define a component:

class Greeter extends React.Component { 
  render () {
     return <h3>Hello, {this.props.name}!</h3>;
   } 
}  

In React, React elements can represent DOM elements or React components:

const helloElement = <Greeter name="{user.name}"/>; 

Also, real React apps are in fact composed of reusable components and elements, which are then rendered in a specific DOM element. This component model is very powerful and has some similarity to the notion of nested custom controls in ASP.NET, but is entirely implemented on the client side:

class Hello extends React.Component { 
  render () {
     return <h3>Hello, {this.props.name}!</h3>;
   } 
}  
 
class HelloMakers...