A Pen by Dan Abramov on CodePen.
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May 16, 2018 21:09
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| <div id="root"> | |
| <!-- This div's content will be managed by React. --> | |
| </div> |
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| const scaleNames = { | |
| c: 'Celsius', | |
| f: 'Fahrenheit' | |
| }; | |
| function toCelsius(fahrenheit) { | |
| return (fahrenheit - 32) * 5 / 9; | |
| } | |
| function toFahrenheit(celsius) { | |
| return (celsius * 9 / 5) + 32; | |
| } | |
| function tryConvert(temperature, convert) { | |
| const input = parseFloat(temperature); | |
| if (Number.isNaN(input)) { | |
| return ''; | |
| } | |
| const output = convert(input); | |
| const rounded = Math.round(output * 1000) / 1000; | |
| return rounded.toString(); | |
| } | |
| function BoilingVerdict(props) { | |
| if (props.celsius >= 100) { | |
| return <p>The water would boil.</p>; | |
| } | |
| return <p>The water would not boil.</p>; | |
| } | |
| class TemperatureInput extends React.Component { | |
| constructor(props) { | |
| super(props); | |
| this.handleChange = this.handleChange.bind(this); | |
| } | |
| handleChange(e) { | |
| this.props.onTemperatureChange(e.target.value); | |
| } | |
| render() { | |
| const temperature = this.props.temperature; | |
| const scale = this.props.scale; | |
| return ( | |
| <fieldset> | |
| <legend>Enter temperature in {scaleNames[scale]}:</legend> | |
| <input value={temperature} | |
| onChange={this.handleChange} /> | |
| </fieldset> | |
| ); | |
| } | |
| } | |
| class Calculator extends React.Component { | |
| constructor(props) { | |
| super(props); | |
| this.handleCelsiusChange = this.handleCelsiusChange.bind(this); | |
| this.handleFahrenheitChange = this.handleFahrenheitChange.bind(this); | |
| this.state = {temperature: '', scale: 'c'}; | |
| } | |
| handleCelsiusChange(temperature) { | |
| this.setState({scale: 'c', temperature}); | |
| } | |
| handleFahrenheitChange(temperature) { | |
| this.setState({scale: 'f', temperature}); | |
| } | |
| render() { | |
| const scale = this.state.scale; | |
| const temperature = this.state.temperature; | |
| const celsius = scale === 'f' ? tryConvert(temperature, toCelsius) : temperature; | |
| const fahrenheit = scale === 'c' ? tryConvert(temperature, toFahrenheit) : temperature; | |
| return ( | |
| <div> | |
| <TemperatureInput | |
| scale="c" | |
| temperature={celsius} | |
| onTemperatureChange={this.handleCelsiusChange} /> | |
| <TemperatureInput | |
| scale="f" | |
| temperature={fahrenheit} | |
| onTemperatureChange={this.handleFahrenheitChange} /> | |
| <BoilingVerdict | |
| celsius={parseFloat(celsius)} /> | |
| </div> | |
| ); | |
| } | |
| } | |
| ReactDOM.render( | |
| <Calculator />, | |
| document.getElementById('root') | |
| ); |
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| <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.3.1/react.js"></script> | |
| <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.3.1/react-dom.js"></script> |
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