📘The missing manual of upgrading ES5 React to ES6+
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README.md
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README.md

ES6 and beyond is very popular.

JS is also unlike any other language in that the experimentation occurs on massive scale thanks to transpilers. Never happened before. -- Dan Abramov

React is a declarative, efficient, and flexible JavaScript library for building user interfaces.

In the earlier days of React development, many programmes were written in ES5. Howerver, as ES6 and beyond is more widely accepted now and with the help of transpiler tools like Babel, we can gradually retire some ES5 code and adopt some new JavaScript features in React development.

Here is a check list to help you translate your ES5 code to ES next in React. You are welcome to contribute with more items provided below.

Quick links

  1. require => import
  2. createClass => extends React.Component
  3. module.exports => export default
  4. name function() => name()
  5. getDefaultProps and propTypes
  6. getInitialState
  7. destructuring & spread attributes
  8. use arrow functions

require => import

ES5

//ES5
var React = require("react");  
var PropTypes = React.PropTypes;

ES6

import React, { Component, PropTypes } from 'react';

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createClass => extends React.Component

ES5

var Mycomponent = React.createClass({
  render: function() {
    return (
      <div>ES5</div>
    );
  },
});

ES6

class Mycomponent extends React.Component {
  render() {
    return (
      <div>ES6</div>
    );
  }
}

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module.exports => export default

ES5

var Mycomponent = React.createClass({
  render: function() {
    return (
      <div>ES5</div>
    );
  },
});

module.exports = Mycomponent;

ES6

export default class Mycomponent extends React.Component {
  render() {
    return (
      <div>ES6</div>
    );
  }
}

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name function() => name()

ES5

var Mycomponent = React.createClass({
  componentWillMount: function(){

  },
  render: function() {
    return (
      <div>ES5</div>
    );
  },
});

module.exports = Mycomponent;

ES6

export default class Mycomponent extends React.Component {
  componentWillMount() {

  }
  render() {
    return (
      <div>ES6</div>
    );
  }
}

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getDefaultProps and propTypes

ES5

var Video = React.createClass({
    getDefaultProps: function() {
        return {
            autoPlay: false,
            maxLoops: 10,
        };
    },
    propTypes: {
        autoPlay: React.PropTypes.bool.isRequired,
        maxLoops: React.PropTypes.number.isRequired,
        posterFrameSrc: React.PropTypes.string.isRequired,
        videoSrc: React.PropTypes.string.isRequired,
    },
    render: function() {
        return (
            <View />
        );
    },
});

ES6

class Video extends React.Component {
  render() {
      return (
          <View />
      );
  }
}
Video.defaultProps = {
    autoPlay: false,
    maxLoops: 10,
};
Video.propTypes = {
    autoPlay: React.PropTypes.bool.isRequired,
    maxLoops: React.PropTypes.number.isRequired,
    posterFrameSrc: React.PropTypes.string.isRequired,
    videoSrc: React.PropTypes.string.isRequired,
};

ES future proposals:

class Video extends React.Component {
  static defaultProps = {
    autoPlay: false,
    maxLoops: 10,
  }
  static propTypes = {
    autoPlay: React.PropTypes.bool.isRequired,
    maxLoops: React.PropTypes.number.isRequired,
    posterFrameSrc: React.PropTypes.string.isRequired,
    videoSrc: React.PropTypes.string.isRequired,
  }
  state = {
    loopsRemaining: this.props.maxLoops,
  }
}

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getInitialState

ES5

var Header = React.createClass({
  getInitialState: function() {
    return {
      title: this.props.title
    };
  },
});

ES6

export default class Header extends Component {
  constructor(props) {
    super(props);
    this.state = {
      title: props.title
    };
  }
}

ES future proposals:

export default class Header extends Component {
  state = {
    title: this.props.title
  };
    
  // followed by constructor...
}

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destructuring & spread attributes

class AutoloadingPostsGrid extends React.Component {
  render() {
    var {
      className,
      ...others,  // contains all properties of this.props except for className
    } = this.props;
    return (
      <div className={className}>
        <PostsGrid {...others} />
        <button onClick={this.handleLoadMoreClick}>Load more</button>
      </div>
    );
  }
}

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use arrow functions

Stateless component:

function App() {
  return (
    <div>
      <MyComponent />
    </div>
  );
}

Using Arrow function:

const App = () => (
  <div>
    <MyComponent />
  </div>
);

Using Arrow funtion with Destructuring function arguments:

const App = ({className, ...rest}) => (
  <div className={classnames(className)} {...rest}>
    <MyComponent />
  </div>
);

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Reference

Roadmap

  • Include all ES5 to ES6+ instructions for React
  • We may Implement ESlint plugin like ESlint-Plugin-React-5-to-6
  • We may Include instructions for configuring Babel with different stages

License

MIT