Manage React Component State with setState

Can you explain why the need to use this.update.bind(this) in the onChange attribute?

Can you explain why the need to use this.update.bind(this) in the onChange attribute?

Previously with React.createClass you would get autobinding. When you use es6 classes, this is no longer the case, so you need to explicitly bind the this scope of event handler functions. People will also do this in the constructor or through a more "es7" style property binding.

    constructor(props) {
        super(props);
        this.update = this.update.bind(this);
    }

MyComponent extends React.Component {
      
    update = () => this. update();

    render() {
    // ...

Which is the preferred way?

I would love a short tutorial about this.

I was trying to use ES7 style and was getting a syntax error..Is there anything I am doing incorrectly

class App extends React.Component { ... update = () => this.updateEnteredText(); updateEnteredText(e){ ... } render() { .....

_bind(...methods) {
  methods.forEach( (method) => this[method] = this[method].bind(this) );
 }

I am doing it this way and then inside constructor this._bind('methodName1','methodName2');

Could I please ask which editor (Atom?) and what plugins you are using? It is like magic and I'd love to make those efficiency gains!

I had some trouble with this because the code in the video does not match the code under Code. I was able to resolve it by adding:

import ReactDOM from 'react-dom';

and

changing:

export default App

to

ReactDOM.render(<App />, document.getElementById('app'));

The JSBin HTML file has script links to fb.me for react and react-dom, so that it does work there, but that is not part of the course lesson.

In further investigation, I found on the github repo for lesson 4 that main.js had been returned to its original state. In one of the earlier lessons, he deletes several lines, but never indicates in subsequent lessons that he put them back.

Thank you for this, this worked for me.

I've got the code for this part working, however in the browser console I see

B:\Projects\JS\react-learning\node_modules\react-error-overlay\lib\overlay.js:66
Uncaught TypeError: Cannot read property 'error' of undefined
 at renderErrorByIndex (B:\Projects\JS\react-learning\node_modules\react-error-overlay\lib\overlay.js:66)
at switchError (B:\Projects\JS\react-learning\node_modules\react-error-overlay\lib\overlay.js:86)
at shortcutHandler (B:\Projects\JS\react-learning\node_modules\react-error-overlay\lib\overlay.js:145)
at keyHandler (B:\Projects\JS\react-learning\node_modules\react-error-overlay\lib\effects\shortcuts.js:17)

Not sure what is causing this. My code looks like the following:

import React from 'react';
import PropTypes from 'prop-types'; // React.PropTypes is deprecated apparently

class App extends React.Component {
    constructor(){
        super();
        this.state =  {
            txt: 'this is dynamic text'
        }
    }

    update( e ){
        this.setState({txt: e.target.value})
    }

    render() {
        let txtProp = this.props.txt;
        let numProp = this.props.cat;
        return ( 
            <div>
                <h1>Hello World - {txtProp} + {numProp} </h1>
                <input type="text" onChange={this.update.bind(this)}/>
                <h2>{this.state.txt}</h2>
            </div>
        )
    }
}

App.propTypes = {
    txt: PropTypes.string,
    cat: PropTypes.number.isRequired
}

App.defaultProps = {
    txt: "default text"
}

// const App = () => <h1>Hello Stateless</h1>

export default App