ReactJS : writing in ES6

12 Feb 2016

When you are new to ES6 syntax with react here is certain things that are different from ES5 syntax.

Extend from React.Component

In ES5 syntax, we use React.createClass create component where as along with ES6 syntax you can extends the component from React.Component.

As per ES5

var React = require('react');

var Comp = React.createClass({
  render() {
    return (<div>Comp with ES5</div>);
  }
})

Where as in ES6

import React, {Component} from 'react';

class Comp extends Component {
  render() {
    return (<div>Comp with ES5</div>);
  }
}

Use constructor instead of getInitialState

In ES5 with React.createClass we usually use getInitialState method to specify the initial state of the component. But with ES6 class syntax you don’t need getInitialState method. You set the initial state in constructor itself.

import React, {Component} from 'react';

class Comp extends Component {
  constructor() {
    super();
    this.state = {
      name: "some name"
    };
  }
  render() {
    return (<div>Comp with ES5 :: {this.state.name}</div>);
  }
}

Use constructor to make ajax calls

Also if you want to make any ajax calls when component is loading you can do that as well in the constructor.

import React, {Component} from 'react';

class Comp extends Component {
  constructor() {
    super();
    this.getData();
  }
  getData() {
    // make ajax call
  }
  render() {
    return (<div>Comp with ES5 :: {this.state.name}</div>);
  }
}

You don’t need to to call getData in componentDidMount.

Specifing propTypes

When using React.createClass with ES5 we can specify the propTypes like

var React = require('react');

var Comp = React.createClass({
  propTypes: {
    name: React.PropTypes.string
  },
  render() {
    return (<div>Comp with ES5 {this.props.name}</div>);
  }
})

But when using ES6 it’s bit different

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

class Comp extends Component {
  render() {
    return (<div>Comp with ES5 :: {this.props.name}</div>);
  }
}

// specify proptypes in class
Comp.propTypes = {
  name: PropTypes.string
}

Comp.defaultProps = {
  name: ""
}

Mixins are supported with ES6 classes

Since mixins are not supportes with ES6 classes, we need to use Higher-Order Components to reuse functionalities across components.

Use .bind(this) on methods

ES6 classes won’t bind the methods with it’s instance. You need to explicity bind with instance using .bind(this)

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

class Comp extends Component {
  getData() {
    // make ajax call
  }
  onClick() {
    this.getData();
  }
  render() {
    return (<div onClick={this.onClick.bind(this)}>Comp with ES5 :: {this.props.name}</div>);
  }
}

If you didn’t bind this.onClick.bind(this) the above code will throw TypeError: this.getData is not a function.

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