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Index.js

Our app lives in the /src folder index.js being is the main entry point for our app. 
 
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import './index.css';

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

Application

Every React application has at least one component: the root component, named App. The App component controls the view through JSX template, with return(). 
 
import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';

class App extends Component {
    render() {

        return (
            <div className="App">
                <div className="App-header">
                    <img src={logo} className="App-logo" alt="logo" />
                    <h2>My React App</h2>
                </div>
            </div>
        );
    }
}

export default App;

Products.js

Note the naming convension for the component file. The first letter must be uppercase. 
 
import React, { Component } from 'react';
class Products extends Component {
    render() {
        return (
            <h2>Products</h2>
        );
    }
}
export default Products;

Root Element

Components must return a single root element. This code will throw an error. 
 
class Products extends Component {
    render() {
        return (
            <h2>Products</h2>
            <h2>Courses</h2> // error
        );
    }
}

Import

Import and add Product to the template. We can also render Products many times. 
 
import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';

import Products from './Products'; // import component

class App extends Component {
    render() {
        return (
            <div className="App">
              <div className="App-header">
              <img src={logo} className="App-logo" />
              <h2>My React App</h2>
              <Products /> // render products
              <Products />
              <Products />
              </div>
            </div>
        );
    }
}
export default App;

Embeded Javascript

We can embed Javascript template string into JSX using wrapping it in curly braces. Key should be unique strings (most often you would use ids). 
 
import React, { Component } from 'react';
class Products extends Component {
    render() {

        // array products
        const products = ["Learning React", "Pro React"];
        // ES6 arrow function (product) =>
        const listProducts = products.map((product) =>
            <li key={product.toString()}>{product}</li>
        );

        return (
            <div>
                <ul>{listProducts}</ul> // render products
            </div>
        );
    }
}
export default Products;




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