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This provides an easy way to indicate that components should only rerender when given new props, like PureRenderMixin. If you rely on mutation in your React components, you can continue to use `React.Component`. Inheriting from `React.PureComponent` indicates to React that your component doesn't need to rerender when the props are unchanged. We'll compare the old and new props before each render and short-circuit if they're unchanged. It's like an automatic shouldComponentUpdate.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,31 @@ | ||
| /** | ||
| * Copyright 2013-present, Facebook, Inc. | ||
| * All rights reserved. | ||
| * | ||
| * This source code is licensed under the BSD-style license found in the | ||
| * LICENSE file in the root directory of this source tree. An additional grant | ||
| * of patent rights can be found in the PATENTS file in the same directory. | ||
| * | ||
| * @providesModule ReactPureComponent | ||
| */ | ||
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| 'use strict'; | ||
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| var ReactComponent = require('ReactComponent'); | ||
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| /** | ||
| * Base class helpers for the updating state of a component. | ||
| */ | ||
| function ReactPureComponent(props, context, updater) { | ||
| ReactComponent.call(this, props, context, updater); | ||
| } | ||
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| function ComponentDummy() {} | ||
| ComponentDummy.prototype = ReactComponent.prototype; | ||
| ReactPureComponent.prototype = new ComponentDummy(); | ||
| ReactPureComponent.prototype.constructor = ReactPureComponent; | ||
| // Avoid an extra prototype jump for these methods. | ||
| Object.assign(ReactPureComponent.prototype, ReactComponent.prototype); | ||
| ReactPureComponent.prototype.isPureReactComponent = true; | ||
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| module.exports = ReactPureComponent; |
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src/isomorphic/modern/class/__tests__/ReactPureComponent-test.js
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
| /** | ||
| * Copyright 2013-present, Facebook, Inc. | ||
| * All rights reserved. | ||
| * | ||
| * This source code is licensed under the BSD-style license found in the | ||
| * LICENSE file in the root directory of this source tree. An additional grant | ||
| * of patent rights can be found in the PATENTS file in the same directory. | ||
| * | ||
| * @emails react-core | ||
| */ | ||
|
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| 'use strict'; | ||
|
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| var React; | ||
| var ReactDOM; | ||
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| describe('ReactPureComponent', function() { | ||
| beforeEach(function() { | ||
| React = require('React'); | ||
| ReactDOM = require('ReactDOM'); | ||
| }); | ||
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| it('should render', function() { | ||
| var renders = 0; | ||
| class Component extends React.PureComponent { | ||
| constructor() { | ||
| super(); | ||
| this.state = {type: 'mushrooms'}; | ||
| } | ||
| render() { | ||
| renders++; | ||
| return <div>{this.props.text[0]}</div>; | ||
| } | ||
| } | ||
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| var container = document.createElement('div'); | ||
| var text; | ||
| var component; | ||
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| text = ['porcini']; | ||
| component = ReactDOM.render(<Component text={text} />, container); | ||
| expect(container.textContent).toBe('porcini'); | ||
| expect(renders).toBe(1); | ||
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| text = ['morel']; | ||
| component = ReactDOM.render(<Component text={text} />, container); | ||
| expect(container.textContent).toBe('morel'); | ||
| expect(renders).toBe(2); | ||
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| text[0] = 'portobello'; | ||
| component = ReactDOM.render(<Component text={text} />, container); | ||
| expect(container.textContent).toBe('morel'); | ||
| expect(renders).toBe(2); | ||
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| // Setting state without changing it doesn't cause a rerender. | ||
| component.setState({type: 'mushrooms'}); | ||
| expect(container.textContent).toBe('morel'); | ||
| expect(renders).toBe(2); | ||
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| // But changing state does. | ||
| component.setState({type: 'portobello mushrooms'}); | ||
| expect(container.textContent).toBe('portobello'); | ||
| expect(renders).toBe(3); | ||
| }); | ||
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| it('can override shouldComponentUpdate', function() { | ||
| var renders = 0; | ||
| class Component extends React.PureComponent { | ||
| render() { | ||
| renders++; | ||
| return <div />; | ||
| } | ||
| shouldComponentUpdate() { | ||
| return true; | ||
| } | ||
| } | ||
| var container = document.createElement('div'); | ||
| ReactDOM.render(<Component />, container); | ||
| ReactDOM.render(<Component />, container); | ||
| expect(renders).toBe(2); | ||
| }); | ||
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| it('extends React.Component', function() { | ||
| var renders = 0; | ||
| class Component extends React.PureComponent { | ||
| render() { | ||
| expect(this instanceof React.Component).toBe(true); | ||
| expect(this instanceof React.PureComponent).toBe(true); | ||
| renders++; | ||
| return <div />; | ||
| } | ||
| } | ||
| ReactDOM.render(<Component />, document.createElement('div')); | ||
| expect(renders).toBe(1); | ||
| }); | ||
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| }); |
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