eslint-plugin-class-prefer-methods

Eslint plugin to report not-needed usage of arrow functions instead of methods in a React Component class. It also throws an error if you pass a class method as callback to some children

Install

npm i --save-dev eslint-plugin-class-prefer-methods

Usage

In your .eslintrc:

{
  "plugins": [
    "class-prefer-methods"
  ],
  "rules": {
    "class-prefer-methods/prefer-methods": 2
  }
}

Why

Arrow function properties are automatically binded to this. This is really handy when you need to pass it as a callback to a children, but it's not necessary in most cases and it impacts performances: the RAM occupied by the component and the JS time to instantiate it are both higher.

Examples

Example of incorrect code for "class-prefer-methods/prefer-methods": 2 rule:

class Example extends React.Component {
 
  state = { clicked: false }
 
  // this could safely be a class method 
  shouldRender = () => {
    return this.props.shouldRender === true;
  }
  
  // this should be an arrow-function property as it's passed as callback to a children
  onClick() {
    this.setState({ clicked: true })
  }
  
  render() {
    if (!this.shouldRender()) {
      return null;
    }
    
    return <div onClick={this.onClick} />;
  }
 
}

Example of correct code for "class-prefer-methods/prefer-methods": 2 rule:

class Example extends React.Component {
 
  state = { clicked: false }
 
  // class methods are lighter
  shouldRender() {
    return this.props.shouldRender === true;
  }
  
  // callbacks that use "this" must be arrow-functions to work properly
  onClick = () => {
    this.setState({ clicked: true })
  }
  
  render() {
    if (!this.shouldRender()) {
      return null;
    }
    
    return <div onClick={this.onClick} />;
  }
 
}