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How to avoid binding by using arrow functions in callbacks in ReactJS?

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  • Last Updated : 18 Feb, 2022

In React class-based components when we use event handler callbacks, it is very important to give special attention to the ‘this’ keyword. In these cases the context this is undefined when the callback function actually gets invoked that’s why we have to bind the context of this. Now if binding all the methods of each class is very annoying. Instead of binding we can use the inline arrow function since the arrow function does not have its own value of this, it uses the parent or public value. Using the inline arrow function we can get rid of annoying method binding every time and also the code looks very packed and organized.

Example 1: This example illustrates how to use arrow functions in callbacks

index.js:

  •  

Javascript




import React from 'react'
import ReactDOM from 'react-dom'
import App from './App'
 
ReactDOM.render(<App />, document.querySelector('#root'))


  •  

App.js : 

  •  

Javascript




import React, { Component } from 'react'
 
class App extends Component {
  // Default props
  static defaultProps = {
    courseContent : [
      'JSX', 'React Props', 'React State', 'React Lifecycle Methods',
      'React Event Handlers', 'React Router', 'React Hooks', 'Readux',
      'React Context'
    ]
  }
   
  constructor(props){
    super(props)
     
    // Set initial state
    this.state = {msg : 'React Course', content:''}
  }
 
  // Return an unordered list of contents
  renderContent(){
    return (
      <ul>
        {/* map over all the contents and
            return some JSX for each  */}
        {this.props.courseContent.map(content => (
          <li>{content}</li>
        ))}
      </ul>
    )
  }
   
  render(){
    const button = !this.state.content &&
    <button
      // Arrow function in callback
      onClick={() => {
        // Update state
        this.setState({
          msg : 'Course Content',
          content : this.renderContent()
        })
      }}
    >
      Click here to know contents!
    </button>
    return (
      <div>
         
 
<p>{this.state.msg}</p>
 
 
         
 
<p>{this.state.content}</p>
 
 
        {button}
      </div>
    )
  }
}
 
export default App


  •  

Output :

Example 2 :

index.js : 

  •  

Javascript




import React from 'react'
import ReactDOM from 'react-dom'
import App from './App'
 
ReactDOM.render(<App />, document.querySelector('#root'))


  •  

App.js : 

  •  

Javascript




import React, { Component } from 'react'
 
class App extends Component{
  // Default props
  static defaultProps = {
    name : ['John', 'Alex', 'Bob']
  }
  constructor(props){
    super(props)
    // Nnitialize count state
    this.state = {msg : 'Hi There', count:0}
  }
 
  render(){
    return(
      <div>
        <h3>Greetings!</h3>    
         
 
<p>{this.state.msg}</p>
 
 
        <button
          // Arrow function in callback
          // does not required explicit binding
          onClick={() => {
            this.setState(st => (
              st.msg = `${st.msg}, ${this.props.name[st.count]}`,
              st.count += 1
            ))
          }}
        >
          Say greeting to employees!
        </button>
      </div>   
    
  }
}
export default App


  •  

Output :


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