react源码解析19.手写迷你版react-低调大师

react源码解析19.手写迷你版react

2021-06-24 528

## react源码解析19.手写迷你版react #### 视频课程（高效学习）：[进入课程](https://xiaochen1024.com/series/60b1b600712e370039088e24/60b1b636712e370039088e25) #### 课程目录： [1.开篇介绍和面试题](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b311cf10a4003b634719) [2.react的设计理念](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b31ccf10a4003b63471a) [3.react源码架构](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b328cf10a4003b63471b) [4.源码目录结构和调试](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b32ecf10a4003b63471c) [5.jsx&核心api](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b334cf10a4003b63471d) [6.legacy和concurrent模式入口函数](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b33acf10a4003b63471e) [7.Fiber架构](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b340cf10a4003b63471f) [8.render阶段](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b348cf10a4003b634720) [9.diff算法](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b354cf10a4003b634721) [10.commit阶段](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b360cf10a4003b634722) [11.生命周期](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b367cf10a4003b634723) [12.状态更新流程](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b36ecf10a4003b634724) [13.hooks源码](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b374cf10a4003b634725) [14.手写hooks](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b37acf10a4003b634726) [15.scheduler&Lane](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b556cf10a4003b634727) [16.concurrent模式](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b55ccf10a4003b634728) [17.context](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b564cf10a4003b634729) [18事件系统](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b56ccf10a4003b63472a) [19.手写迷你版react](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b57bcf10a4003b63472b) [20.总结&第一章的面试题解答](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b581cf10a4003b63472c) [21.demo](https://xiaochen1024.com/courseware/60b1b2f6cf10a4003b634718/60b1b587cf10a4003b63472d) #### 迷你react和真正的源码有哪些区别呢 - 在render阶段我们遍历了整颗Fiber树，在源码中如果节点什么都没改变会命中优化的逻辑，然后跳过这个节点的遍历 - commit我们也遍历了整颗Fiber树，源码中只遍历带有effect的Fiber节点，也就是遍历effectList - 每次遍历的时候我们都是新建节点，源码中某些条件会复用节点 - 没有用到优先级第一步：渲染器和入口函数 ```js const React = { createElement, render, }; const container = document.getElementById("root"); const updateValue = (e) => { rerender(e.target.value); }; const rerender = (value) => { const element = (

Hello {value}

); React.render(element, container); }; rerender("World"); ``` 第二步：创建dom节点函数 ```js /创建element function createElement(type, props, ...children) { return { type, props: { ...props, children: children.map((child) => (typeof child === "object" ? child : createTextElement(child))), }, }; } //创建text类型 function createTextElement(text) { return { type: "TEXT_ELEMENT", props: { nodeValue: text, children: [], }, }; } //创建dom function createDom(fiber) { const dom = fiber.type === "TEXT_ELEMENT" ? document.createTextNode("") : document.createElement(fiber.type); updateDom(dom, {}, fiber.props); return dom; } ``` 第三步：更新节点函数 ```js const isEvent = (key) => key.startsWith("on"); const isProperty = (key) => key !== "children" && !isEvent(key); const isNew = (prev, next) => (key) => prev[key] !== next[key]; const isGone = (prev, next) => (key) => !(key in next); //更新节点属性 function updateDom(dom, prevProps, nextProps) { //删除老的事件 Object.keys(prevProps) .filter(isEvent) .filter((key) => !(key in nextProps) || isNew(prevProps, nextProps)(key)) .forEach((name) => { const eventType = name.toLowerCase().substring(2); dom.removeEventListener(eventType, prevProps[name]); }); // 删除旧属性 Object.keys(prevProps) .filter(isProperty) .filter(isGone(prevProps, nextProps)) .forEach((name) => { dom[name] = ""; }); // 设置新属性 Object.keys(nextProps) .filter(isProperty) .filter(isNew(prevProps, nextProps)) .forEach((name) => { dom[name] = nextProps[name]; }); // 增加新事件 Object.keys(nextProps) .filter(isEvent) .filter(isNew(prevProps, nextProps)) .forEach((name) => { const eventType = name.toLowerCase().substring(2); dom.addEventListener(eventType, nextProps[name]); }); } ``` 第四步：render阶段 ```js //render阶段 function performUnitOfWork(fiber) { if (!fiber.dom) { fiber.dom = createDom(fiber); } const elements = fiber.props.children; reconcileChildren(fiber, elements); if (fiber.child) { return fiber.child; } let nextFiber = fiber; while (nextFiber) { if (nextFiber.sibling) { return nextFiber.sibling; } nextFiber = nextFiber.parent; } } //调协节点 function reconcileChildren(wipFiber, elements) { let index = 0; let oldFiber = wipFiber.alternate && wipFiber.alternate.child; let prevSibling = null; while (index < elements.length || (oldFiber !== null && oldFiber !== undefined)) { const element = elements[index]; let newFiber = null; const sameType = oldFiber && element && element.type === oldFiber.type; if (sameType) { newFiber = { type: oldFiber.type, props: element.props, dom: oldFiber.dom, parent: wipFiber, alternate: oldFiber, effectTag: "UPDATE", }; } if (element && !sameType) { newFiber = { type: element.type, props: element.props, dom: null, parent: wipFiber, alternate: null, effectTag: "PLACEMENT", }; } if (oldFiber && !sameType) { oldFiber.effectTag = "DELETION"; deletions.push(oldFiber); } if (oldFiber) { oldFiber = oldFiber.sibling; } if (index === 0) { wipFiber.child = newFiber; } else if (element) { prevSibling.sibling = newFiber; } prevSibling = newFiber; index++; } } ``` 第五步：commit阶段 ```js //commit阶段 function commitRoot() { deletions.forEach(commitWork); commitWork(wipRoot.child); currentRoot = wipRoot; wipRoot = null; } //操作真实dom function commitWork(fiber) { if (!fiber) { return; } const domParent = fiber.parent.dom; if (fiber.effectTag === "PLACEMENT" && fiber.dom !== null) { domParent.appendChild(fiber.dom); } else if (fiber.effectTag === "UPDATE" && fiber.dom !== null) { updateDom(fiber.dom, fiber.alternate.props, fiber.props); } else if (fiber.effectTag === "DELETION") { domParent.removeChild(fiber.dom); } commitWork(fiber.child); commitWork(fiber.sibling); } ``` 第六步：开始调度 ```js //渲染开始的入口 function render(element, container) { wipRoot = { dom: container, props: { children: [element], }, alternate: currentRoot, }; deletions = []; nextUnitOfWork = wipRoot; } //调度函数 function workLoop(deadline) { let shouldYield = false; while (nextUnitOfWork && !shouldYield) { //render阶段 nextUnitOfWork = performUnitOfWork(nextUnitOfWork); shouldYield = deadline.timeRemaining() < 1; } if (!nextUnitOfWork && wipRoot) { commitRoot(); //commit阶段 } requestIdleCallback(workLoop); //空闲调度 } requestIdleCallback(workLoop); ``` 完整代码 ```js //创建element function createElement(type, props, ...children) { return { type, props: { ...props, children: children.map((child) => (typeof child === "object" ? child : createTextElement(child))), }, }; } //创建text类型 function createTextElement(text) { return { type: "TEXT_ELEMENT", props: { nodeValue: text, children: [], }, }; } //创建dom function createDom(fiber) { const dom = fiber.type === "TEXT_ELEMENT" ? document.createTextNode("") : document.createElement(fiber.type); updateDom(dom, {}, fiber.props); return dom; } const isEvent = (key) => key.startsWith("on"); const isProperty = (key) => key !== "children" && !isEvent(key); const isNew = (prev, next) => (key) => prev[key] !== next[key]; const isGone = (prev, next) => (key) => !(key in next); //更新节点属性 function updateDom(dom, prevProps, nextProps) { //删除老的事件 Object.keys(prevProps) .filter(isEvent) .filter((key) => !(key in nextProps) || isNew(prevProps, nextProps)(key)) .forEach((name) => { const eventType = name.toLowerCase().substring(2); dom.removeEventListener(eventType, prevProps[name]); }); // 删除旧属性 Object.keys(prevProps) .filter(isProperty) .filter(isGone(prevProps, nextProps)) .forEach((name) => { dom[name] = ""; }); // 设置新属性 Object.keys(nextProps) .filter(isProperty) .filter(isNew(prevProps, nextProps)) .forEach((name) => { dom[name] = nextProps[name]; }); // 增加新事件 Object.keys(nextProps) .filter(isEvent) .filter(isNew(prevProps, nextProps)) .forEach((name) => { const eventType = name.toLowerCase().substring(2); dom.addEventListener(eventType, nextProps[name]); }); } //commit阶段 function commitRoot() { deletions.forEach(commitWork); commitWork(wipRoot.child); currentRoot = wipRoot; wipRoot = null; } //操作真实dom function commitWork(fiber) { if (!fiber) { return; } const domParent = fiber.parent.dom; if (fiber.effectTag === "PLACEMENT" && fiber.dom !== null) { domParent.appendChild(fiber.dom); } else if (fiber.effectTag === "UPDATE" && fiber.dom !== null) { updateDom(fiber.dom, fiber.alternate.props, fiber.props); } else if (fiber.effectTag === "DELETION") { domParent.removeChild(fiber.dom); } commitWork(fiber.child); commitWork(fiber.sibling); } let nextUnitOfWork = null; let currentRoot = null; let wipRoot = null; let deletions = null; //渲染开始的入口 function render(element, container) { wipRoot = { dom: container, props: { children: [element], }, alternate: currentRoot, }; deletions = []; nextUnitOfWork = wipRoot; } //调度函数 function workLoop(deadline) { let shouldYield = false; while (nextUnitOfWork && !shouldYield) { //render阶段 nextUnitOfWork = performUnitOfWork(nextUnitOfWork); shouldYield = deadline.timeRemaining() < 1; } if (!nextUnitOfWork && wipRoot) { commitRoot(); //commit阶段 } requestIdleCallback(workLoop); //空闲调度 } requestIdleCallback(workLoop); //render阶段 function performUnitOfWork(fiber) { if (!fiber.dom) { fiber.dom = createDom(fiber); } const elements = fiber.props.children; reconcileChildren(fiber, elements); if (fiber.child) { return fiber.child; } let nextFiber = fiber; while (nextFiber) { if (nextFiber.sibling) { return nextFiber.sibling; } nextFiber = nextFiber.parent; } } //调协节点 function reconcileChildren(wipFiber, elements) { let index = 0; let oldFiber = wipFiber.alternate && wipFiber.alternate.child; let prevSibling = null; while (index < elements.length || (oldFiber !== null && oldFiber !== undefined)) { const element = elements[index]; let newFiber = null; const sameType = oldFiber && element && element.type === oldFiber.type; if (sameType) { newFiber = { type: oldFiber.type, props: element.props, dom: oldFiber.dom, parent: wipFiber, alternate: oldFiber, effectTag: "UPDATE", }; } if (element && !sameType) { newFiber = { type: element.type, props: element.props, dom: null, parent: wipFiber, alternate: null, effectTag: "PLACEMENT", }; } if (oldFiber && !sameType) { oldFiber.effectTag = "DELETION"; deletions.push(oldFiber); } if (oldFiber) { oldFiber = oldFiber.sibling; } if (index === 0) { wipFiber.child = newFiber; } else if (element) { prevSibling.sibling = newFiber; } prevSibling = newFiber; index++; } } const React = { createElement, render, }; const container = document.getElementById("root"); const updateValue = (e) => { rerender(e.target.value); }; const rerender = (value) => { const element = (

Hello {value}

); React.render(element, container); }; rerender("World"); ```

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原文链接：https://blog.51cto.com/u_11890769/2942846

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低调大师中文资讯倾力打造互联网数据资讯、行业资源、电子商务、移动互联网、网络营销平台。持续更新报道IT业界、互联网、市场资讯、驱动更新,是最及时权威的产业资讯及硬件资讯报道平台。

Flink 常用 API 详解

@[TOC] [还有视频讲解在我的B站-宝哥chbxw](https://www.bilibili.com/video/BV1Ga4y1Y7C4/), 希望大家可以支持一下，谢谢。 # 前言之分层 API Flink 根据抽象程度分层，提供了三种不同的 API。每一种 API 在简洁性和表达力上有着不同的侧重，并且针对不同的应用场景。 ![在这里插入图片描述](https://img-blog.csdnimg.cn/20200622173937180.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d1eGludGRyaA==,size_16,color_FFFFFF,t_70) - **ProcessFunction** 是 Flink 所提供最底层接口。ProcessFunction 可以处理一或两条输入数据流中的单个事件或者归入一个特定窗口内的多个事件。它提供了对于时间和状态的细粒度控制。开发者可以在其中任意地修改状态，也...

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2 --> 简介在数据处理中，Pandas会将无法解析的数据或者缺失的数据使用NaN来表示。虽然所有的数据都有了相应的表示，但是NaN很明显是无法进行数学运算的。本文将会讲解Pandas对于NaN数据的处理方法。 NaN的例子上面讲到了缺失的数据会被表现为NaN，我们来看一个具体的例子：我们先来构建一个DF： In [1]: df = pd.DataFrame(np.random.randn(5, 3), index=['a', 'c', 'e', 'f', 'h'], ...: columns=['one', 'two', 'three']) ...: In [2]: df['four'] = 'bar' In [3]: df['five'] = df['one'] > 0 In [4]: df Out[4]: one two three four five a 0.469112 -0.282863 -1.509059 bar True c -1.135632 1.212112 -0.173215 bar False e 0.119209 -1.044236 -0.86...

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