javascript - React Event Handle OnChange - Stack Overflow

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I am trying to update the title of a header ponent by executing an onchange event in my app.js, but cant seem to bind them correctly. So when user types in input it will show the text in the header ponent.

APP.JS

 import React, { Component } from 'react';

    import './App.css';
    import Header from './Header';

    class App extends Component {

      constructor(props) {
        super(props);
       this.state = {name: "Michael"}

      }

       handleChange(e) {
         const name = e.target.value;
         this.changeTitle(name);
       }

      render() {
        return (
          <div className="App">
            <Header changeTitle={this.changeTitle.bind(this)} title={this.state.name}/>
            <p className="App-intro">
              Type here to change name.
            <input type="text" onChange={this.handleChange.bind(this)}/>
            </p>
          </div>
        );
      }
    }

    export default App;

HEADER.JS

import React, { Component } from 'react';
import logo from './logo.svg';

class Header extends Component {
  changeTitle(name) {
     this.setState({name});
   }
    render() {
        return (
            <div>
                <div className="App-header">
                    <img src={logo} className="App-logo" alt="logo" />
                    <h2>Wele to React {this.props.name}</h2>
                </div>
            </div>
        );
    }
}

export default Header;

I am trying to update the title of a header ponent by executing an onchange event in my app.js, but cant seem to bind them correctly. So when user types in input it will show the text in the header ponent.

APP.JS

 import React, { Component } from 'react';

    import './App.css';
    import Header from './Header';

    class App extends Component {

      constructor(props) {
        super(props);
       this.state = {name: "Michael"}

      }

       handleChange(e) {
         const name = e.target.value;
         this.changeTitle(name);
       }

      render() {
        return (
          <div className="App">
            <Header changeTitle={this.changeTitle.bind(this)} title={this.state.name}/>
            <p className="App-intro">
              Type here to change name.
            <input type="text" onChange={this.handleChange.bind(this)}/>
            </p>
          </div>
        );
      }
    }

    export default App;

HEADER.JS

import React, { Component } from 'react';
import logo from './logo.svg';

class Header extends Component {
  changeTitle(name) {
     this.setState({name});
   }
    render() {
        return (
            <div>
                <div className="App-header">
                    <img src={logo} className="App-logo" alt="logo" />
                    <h2>Wele to React {this.props.name}</h2>
                </div>
            </div>
        );
    }
}

export default Header;

• javascript
• reactjs
• ecmascript-6

Share Improve this question Follow asked May 19, 2017 at 12:29 MichaelhMichaelh 15611 gold badge11 silver badge1111 bronze badges 1

• You need to set state in the Parent ponent and then pass the title as a prop to the header ponent. – Deepak Commented May 19, 2017 at 12:32

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 5

changeTitle function should be defined in the App ponent and not in the Header ponent. In fact you can directly call the changeTitle ponent instead of calling it from the handleChange and in the Header ponent access the prop as this.props.title and not this.props.name

import React, { Component } from 'react';

import './App.css';
import Header from './Header';

class App extends Component {

  constructor(props) {
    super(props);
   this.state = {name: "Michael"}

  }
   changeTitle = (e) =>{
      this.setState({name: e.target.value});
    }

  render() {
    return (
      <div className="App">
        <Header title={this.state.name}/>
        <p className="App-intro">
          Type here to change name.
        <input type="text" onChange={this.changeTitle}/>
        </p>
      </div>
    );
  }
}

export default App;

And use it in your Header as

import React, { Component } from 'react';
import logo from './logo.svg';

class Header extends Component {

    render() {
        return (
            <div>
                <div className="App-header">
                    <img src={logo} className="App-logo" alt="logo" />
                    <h2>Wele to React {this.props.title}</h2>
                </div>
            </div>
        );
    }
}

export default Header;

Working snippet:

    class App extends React.Component {

      constructor(props) {
        super(props);
       this.state = {name: "Michael"}

      }
       changeTitle = (e) =>{
          this.setState({name: e.target.value});
        }
       
      render() {
        return (
          <div className="App">
            <Header title={this.state.name}/>
            <p className="App-intro">
              Type here to change name.
            <input type="text" onChange={this.changeTitle}/>
            </p>
          </div>
        );
      }
    }


    
    class Header extends React.Component {
      
        render() {
            var logo = 'https://processing/tutorials/pixels/imgs/tint1.jpg';
            return (
                <div>
                    <div className="App-header">
                        <img src={logo} className="App-logo" alt="logo" />
                        <h2>Wele to React {this.props.title}</h2>
                    </div>
                </div>
            );
        }
    }
    
ReactDOM.render(<App/>, document.getElementById('app'))

<script src="https://cdnjs.cloudflare./ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare./ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>

You don't need to pass the change event to Header ponent, just pass the data only and do the setState in App ponent.

Reason is you are using Header ponent only to display the header name, so state should be managed by the parent ponent App.

Check the working snippet:

class App extends React.Component {

      constructor(props) {
         super(props);
         this.state = {name: "Michael"}
      }

       handleChange(e) {
          const name = e.target.value;
          this.setState({name});   //do the setState here
       }

      render() {
        return (
          <div className="App">
            <Header title={this.state.name}/>
            <p className="App-intro">
              Type here to change name.
            <input type="text" onChange={this.handleChange.bind(this)}/>
            </p>
          </div>
        );
      }
    }
    class Header extends React.Component {
        render() {
            return (
                <div>
                    <div className="App-header">
                        <img src={''} className="App-logo" alt="logo" />
                        <h2>Wele to React {this.props.title}</h2>
                    </div>
                </div>
            );
        }
    }
    
ReactDOM.render(<App/>, document.getElementById('app'))

<script src="https://cdnjs.cloudflare./ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare./ajax/libs/react/15.1.0/react-dom.min.js"></script>

<div id='app'/>

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