mirror of
https://github.com/kay-is/react-from-zero.git
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103 lines
3.0 KiB
HTML
103 lines
3.0 KiB
HTML
<!doctype html>
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<title>13 Element Refactor - React From Zero</title>
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<script src="https://unpkg.com/react@16.4.0/umd/react.development.js"></script>
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<script src="https://unpkg.com/react-dom@16.4.0/umd/react-dom.development.js"></script>
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<script src="https://unpkg.com/create-react-class@15.6.3/create-react-class.js"></script>
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<script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
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<div id="app"></div>
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<script type="text/babel">
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// Refactoring an element is a bit more tricky
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// First, React decides if a tag is an element by checking its case
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// lower case means element
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// upper case means component
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var element = <div/>
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// becomes
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element = React.createElement("div", null)
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try {
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var component = <Div/>
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// becomes
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component = React.createElement(Div, null)
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} catch(e) {}
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// Second, React converts all events these elements trigger, to
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// synthetic events. This is often not a problem, they are simply events.
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// But you can"t trigger your own.
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// So even if your <Input> component accepts a onClick callback as property
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// You can"t call it with the same event as an <input> element would
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// One approach could be this.
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// We simply implement our own onChange caller
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// Here we create a number input that only calls onChange on number inputs
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// (non-numbers trigger an empty change)
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var NumberInput = createReactClass({
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getInitialState: function() {
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return {value: ""}
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},
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handleInput: function(e) {
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// we could try to modify the event to get or data in
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// but this could mess things up
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// instead we prevent this event from further actions
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e.preventDefault()
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var newNumber = e.target.value
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// filter empty-changes
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if (newNumber.length < 1 || newNumber === this.state.value) return
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this.setState({value: newNumber})
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//then we extract our data and give it to onChange
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this.props.onChange(newNumber)
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},
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render: function () {
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return <input type="number" value={this.state.value} onChange={this.handleInput}/>
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},
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})
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function logChange(v){
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console.log(v)
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}
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// Here we see, that the new NumberInput has a different interface
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// it"s onChange property implies that events will be received, but this isn"t
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// the case. Also, even if we would want to call it like the original input,
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// we would need to use upper case, and wouldn"t win anything
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var reactElement = <div style={{width: 300, margin: "auto"}}>
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<h2>Logging number inputs</h2>
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<h2>Before Refactor</h2>
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<input type="number" onChange={function(e) { logChange(e.target.value) }}/>
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<h2>After Refactor</h2>
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<NumberInput onChange={logChange}/>
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</div>
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ReactDOM.render(reactElement, document.getElementById("app"))
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// Other approaches include not using "default" prop names in the first place
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// onUpdate instead of onChange
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// It could also that a component uses onMouseDown to do something internall
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// and triggers a onChange, which could cause confusion
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// Often components deliver richer interactions than elements in the first place
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// so their prop methods can reflect that with the name
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</script> |