|
| 1 | + |
| 2 | +## 一、组件 |
| 3 | + |
| 4 | +React 定义组件的方式有：`React.Component` 和 `React.PureComponent`。 |
| 5 | + |
| 6 | +### 1.React.Component |
| 7 | + |
| 8 | +通过继承 React 基类进行定义： |
| 9 | + |
| 10 | +```js |
| 11 | +class LEOComponent extends React.Component { |
| 12 | + constructor(props) { |
| 13 | + super(props); |
| 14 | + this.state = { |
| 15 | + }; |
| 16 | + } |
| 17 | +} |
| 18 | +``` |
| 19 | + |
| 20 | +### 2.React.PureComponent |
| 21 | + |
| 22 | +和 `React.Component` |
| 23 | + |
| 24 | +### 3.从源码看两者区别 |
| 25 | + |
| 26 | +以下是两者实现源码： |
| 27 | + |
| 28 | +```js |
| 29 | +function Component(props, context, updater) { |
| 30 | + this.props = props; |
| 31 | + this.context = context; |
| 32 | + this.refs = emptyObject; |
| 33 | + this.updater = updater || ReactNoopUpdateQueue; |
| 34 | +} |
| 35 | + |
| 36 | +Component.prototype.isReactComponent = {}; |
| 37 | +Component.prototype.setState = function(partialState, callback) { |
| 38 | + // 省略... |
| 39 | +}; |
| 40 | +Component.prototype.forceUpdate = function(callback) { |
| 41 | + // 省略... |
| 42 | +}; |
| 43 | + |
| 44 | +function ComponentDummy() {} |
| 45 | +ComponentDummy.prototype = Component.prototype; |
| 46 | + |
| 47 | +function PureComponent(props, context, updater) { |
| 48 | + this.props = props; |
| 49 | + this.context = context; |
| 50 | + this.refs = emptyObject; |
| 51 | + this.updater = updater || ReactNoopUpdateQueue; |
| 52 | +} |
| 53 | +const pureComponentPrototype = (PureComponent.prototype = new ComponentDummy()); |
| 54 | +pureComponentPrototype.constructor = PureComponent; |
| 55 | +Object.assign(pureComponentPrototype, Component.prototype); |
| 56 | +pureComponentPrototype.isPureReactComponent = true; |
| 57 | + |
| 58 | +export {Component, PureComponent}; |
| 59 | +``` |
| 60 | + |
| 61 | +从源码看， `React.Component` 与 `React.PureComponent` 类实现的方式一样，并且`React.PureComponent` 继承于 `React.Component`，但比 `React.Component` 原型链上多了 `isPureReactComponent` 属性。 |
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