Created
October 21, 2018 12:07
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Component lifecycle reset update (set state to old state)
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>Lifecycle reset</title> | |
| <style> | |
| body, textarea { | |
| font-family: Courier; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <div id="app"> | |
| <!-- my app renders here --> | |
| </div> | |
| <script charset="utf-8" crossorigin src="https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.26.0/babel.min.js"></script> | |
| <script crossorigin src="https://unpkg.com/react@16/umd/react.development.js"></script> | |
| <script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script> | |
| <script crossorigin src="https://cdnjs.cloudflare.com/ajax/libs/prop-types/15.6.2/prop-types.min.js"></script> | |
| <script type="text/babel"> | |
| class TextAreaCounter extends React.Component { | |
| constructor(props) { | |
| super(props); | |
| this.state = { | |
| text: props.defaultValue | |
| }; | |
| this._textChange = this._textChange.bind(this); | |
| } | |
| static defaultProps = { | |
| defaultValue: 'default text' | |
| }; | |
| componentDidUpdate(oldProps, oldState) { | |
| if (this.state.text.length > 3) { | |
| console.log('The text is too long, abort, abort!'); | |
| this.setState((state, props) => { | |
| return oldState; | |
| }); | |
| } | |
| }; | |
| _textChange(event) { | |
| this.setState({ | |
| text: event.target.value, | |
| }); | |
| }; | |
| render() { | |
| return ( | |
| <div> | |
| <textarea onChange={this._textChange} value={this.state.text}></textarea> | |
| <h3>{this.state.text.length}</h3> | |
| </div> | |
| ); | |
| }; | |
| } | |
| TextAreaCounter.propTypes = { | |
| defaultValue: PropTypes.string | |
| }; | |
| var myTextAreaCounter = ReactDOM.render( | |
| React.createElement(TextAreaCounter, { | |
| defaultValue: "Bob", | |
| }), | |
| document.getElementById("app") | |
| ); | |
| </script> | |
| </body> | |
| </html> |
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