mirror of
https://github.com/kay-is/react-from-zero.git
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102 lines
3.3 KiB
HTML
102 lines
3.3 KiB
HTML
<!doctype html>
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<title>09 Component Classes - 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/prop-types@15.6.1/prop-types.js"></script>
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<script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
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<script src="https://unpkg.com/create-react-class@15.6.3/create-react-class.js">
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// React.createClass was removed from React 16 and is now their own package
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</script>
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<div id="app"></div>
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<script type="text/babel">
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// Often a component needs to maintain some internal state
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// for example if there is interaction involved
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// in this case a component function is not sufficient
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// the component function can only has properties and no state
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// we need a component class with a render function
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var MyComponent = createReactClass({
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// used for type-checking of the properties
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// same as with the component function
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propTypes: {
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color: PropTypes.string,
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},
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// this method will be called by React
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// before the components gets mounted into the DOM
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getDefaultProps: function() {
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return {color: "green"}
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},
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// this method will be called by React
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// before the components gets mounted into the DOM
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// if this method is missing, this.state will be undefined
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getInitialState: function() {
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// The state can be any JavaScript value, often it is an object
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return {times: 0}
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},
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// this method handles all the clicks on the <span> element
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handleClick: function() {
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// setState() can be called with an object that contains the new state
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// normally this triggers a call of render(), but React can batch multiple
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// calls and defer the render() call (make the call asynchronous)
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// To prevent this, setState can take a callback instead
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// This can lead to unexpected behaviour, if we rely on this.state or
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// this.props for our calculations
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// this.setState({times: this.state.times + 1})
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// The callback version doesn't have this problem
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// The callback gets the right state and props at time of the update
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this.setState(function(prevState, props) {
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return {times: prevState.times + 1}
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})
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},
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// this method will be called by React
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// after the component got mounted into the DOM
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// also every time this.setState() was called
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// it's like the component function from before
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// but without a props argument
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render: function() {
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// using the prop given by the creator of this component
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// properties are now in this.props instead of the props argument
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var style = {color: this.props.color}
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// returning an element with a click-handler and the props and
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// state values. state is stored in this.state
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return (
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<span onClick={this.handleClick} style={style}>
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Clicked {this.state.times} times
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</span>
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)
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},
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})
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// creating some instances of the interactive stateful component class
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// one with default color
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// Everything works exactly like with the simpler component functions
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// The interface has not changed for the user of this component
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var reactElement =
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<div>
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<MyComponent color="red"/>
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<br/>
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<MyComponent color="blue"/>
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<br/>
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<MyComponent/>
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</div>;
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var renderTarget = document.getElementById("app")
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ReactDOM.render(reactElement, renderTarget)
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</script> |