old_contents: import React, { Component } from 'react';
  
  import mockData from '../utils/mockData';
  import Article from './Article';
  
  export default class Main extends Component {
  	
  	constructor(props) {
  		super(props);
  		this.articles = mockData;
  	}
  
  	render() {
  		return (
  			<div className="col-md-8">
  				{ this.articles.map(function(article, index) {
  					return (
  						<Article key={ article.id } article={ article } />
  					);
  				}) }
  			</div>
  		);
  	}
  }
new_contents: import React, { Component } from 'react';
  
  import mockData from '../utils/mockData';
  import Article from './Article';
  
  export default class Main extends Component {
  	
  	constructor(props) {
  		super(props);
  		this.state = {
  			articles: mockData
  		}
  	}
  
  	render() {
  		return (
  			<div className="col-md-8">
  				{ this.state.articles.map(function(article, index) {
  					return (
  						<Article key={ article.id } article={ article } />
  					);
  				}) }
  			</div>
  		);
  	}
  }
subject: set initial state