jsx | 易学教程

JSX简介

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“JSX” JSX就是Javascript和XML结合的一种格式。 React发明了JSX，利用HTML语法来创建虚拟DOM。当遇到<，JSX就当HTML解析，遇到{就当JavaScript解析。 JSX，是一个 JavaScript 的语法扩展。JSX 可以很好地描述 UI 应该呈现出它应有交互的本质形式。 JSX将XML语法直接加入JS中,通过代码而非模板来高效的定义界面。之后JSX通过翻译器转换为纯JS再由浏览器执行。在实际开发中，JSX在产品打包阶段都已经编译成纯JavaScript，JSX的语法不会带来任何性能影响。另外，由于JSX只是一种语法，因此JavaScript的关键字class, for等也不能出现在XML中，而要如例子中所示，使用className, htmlFor代替，这和原生DOM在JavaScript中的创建也是一致的。JSX只是创建虚拟DOM的一种语法格式而已,除了用JSX,我们也可以用JS代码来创建虚拟DOM. “JSX表示对象” React.createElement() 1 const element = ( 2 <h1 className="greeting"> 3 Hello, world! 4 </h1> 5 ); 　等效 1 const element = React.createElement( 2 'h1', 3 {className

React入门-JSX和虚拟dom

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1.JSX理解举例： const element = <h1>Hello, world!</h1>; 这被称为 JSX，是一个 JavaScript 的语法扩展。建议在 React 中配合使用 JSX，JSX 可以生成 React “元素”，而且JSX 可以很好地描述 UI 应该呈现出它应有交互的本质形式。JSX 可能会使人联想到模版语言，但它具有 JavaScript 的全部功能。为什么用JSX? React 认为渲染逻辑本质上与其他 UI 逻辑内在耦合，比如，在 UI 中需要绑定处理事件、在某些时刻状态发生变化时需要通知到 UI，以及需要在 UI 中展示准备好的数据。 React 并没有采用将标记与逻辑进行分离到不同文件这种人为地分离方式，而是通过将二者共同存放在称之为“组件”的松散耦合单元之中，来实现关注点分离。在 JSX 中嵌入表达式 name const name = 'Josh Perez'; const element = <h1>Hello, {name}</h1>; ReactDOM.render( element, document.getElementById('root') ); 2 + 2 ， user.firstName formatName(user) formatName(user) <h1> function formatName

Vue之render渲染函数和JSX的应用

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模板的最大特点是扩展难度大，不易扩展。可能会造成逻辑冗余 <Level :type="1">哈哈</Level> <Level :type="2">哈哈</Level> <Level :type="3">哈哈</Level> Level组件需要对不同的type产生不同的标签 <template> <h1 v-if="type==1"> <slot></slot> </h1> <h2 v-else-if="type==2"> <slot></slot> </h2> <h3 v-else-if="type==3"> <slot></slot> </h3> </template> <script> export default { props: { type: { type: Number } } }; </script> 函数式组件没有模板,只允许提供render函数 export default { render(h) { return h("h" + this.type, {}, this.$slots.default); }, props: { type: { type: Number } } }; 复杂的逻辑变得非常简单使用jsx会让代码看起来更加简洁易于读取 export default { render(h) { const tag = "h" + this.type;

After Effects / ExtendScript: Using libraries and importing .jsx files?

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I am new to After Effects scripting but have much experience with JavaScript in the browser. How do I import .jsx files? Can I use js libraries such as underscore.js etc? What are some good resources for AE scripting? (Ideally infographics projects) To include a .jsx next to your script use: #include "includeme.jsx" EDIT 2: You can also include files using the following syntax: //@include "includeme.jsx" Which (IMHO) is the better way. It wont break a linter and is more javascript-ish. You can use plain old javascript (ES3 Syntax). If the libraries you include use some browser specific js

Setting state in function doesn't trigger a rerender

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问题 I want to make a loading indicator on user login, but for some reason the JSX conditional element does not update: class LoginPage extends Component { constructor (props) { super(props) this.state = { waitingOnLogin: false, ... } this.handleLogin = this.handleLogin.bind(this) } handleLogin (event) { event.preventDefault() this.state.waitingOnLogin = true this.props.userActions.login(this.state.email, this.state.password) } render() { return ( <div className='up'> <form onSubmit={e => this

Need help on React Js

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I am new to React Js and my code is not working. Please have a look below: This is my script file Main.jsx . This file is compiled by react and output is put in main.js file under 'dist' folder. var react = require("react"), reactDom = require("react-dom"); var myComponent = react.createClass({ render: function () { return <div><h4>I am rendered by react.</h4></div>; } }); reactDom.render(<myComponent />, document.getElementById("basicDiv")); It is Index.html <html> <head> <base href="./" /> <title>App title</title> <script src="node_modules/react/dist/react.js"></script> <script src="node

Setting state in function doesn't trigger a rerender

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I want to make a loading indicator on user login, but for some reason the JSX conditional element does not update: class LoginPage extends Component { constructor (props) { super(props) this.state = { waitingOnLogin: false, ... } this.handleLogin = this.handleLogin.bind(this) } handleLogin (event) { event.preventDefault() this.state.waitingOnLogin = true this.props.userActions.login(this.state.email, this.state.password) } render() { return ( <div className='up'> <form onSubmit={e => this.handleLogin(e)}> ... </form> {this.state.waitingOnLogin && <Spinner message='Logging you in'/>} // This

React Accessing a value from an array

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I have a form in React which dynamically adds new input elements. This seems to be working ok but I cant seem to access the input values as shown in this screenshot... I have tried the following console.log(this.state.telephone.name) and... console.log(this.state.telephone.tidx.name) where tidx is the unique key. Here is the constructor... constructor() { super(); this.state = { role: "Installer", name: "", telephoneType: [{ name: "" }], telephone: [{ name: "" }], tidx: "", emailType: [{ email: "" }], email: [{ email: "" }], eidx: "", notes: "" }; } and this is my function to handle the input

06Babel

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感悟把webpack得入口和出口地址进行变更，同时devServer里面contentBase得地址也要变更，这个地址是本地服务器所加载得页面所在得目录 devServer: { contentBase: "./public",//本地服务器所加载的页面所在的目录 } webpack学习：如今这个目录下得webpack.config.js得配置如下 module.exports = { entry: __dirname + "/06Babel/app/main.js", output: { path: __dirname + "/06Babel/public", filename: "bundle.js" }, devtool:"eval-source-map", devServer: { contentBase: "./06Babel/public", //本地服务器所加载的页面所在的目录 historyApiFallback:true,//不跳转 inline:true//实时刷新 } } 新内容：Babel Babel其实是一个编译JavaScript的平台，它可以编译代码帮你达到以下目的：让你能使用最新的JavaScript代码（ES6，ES7...），而不用管新标准是否被当前使用的浏览器完全支持；让你能使用基于JavaScript进行了拓展的语言

Undefined is not a function near _reactNavigation.StackNavigator

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I want to setup a React Native app with a side menu and a tab menu at the same time. I was following this tutorial. My code . I get the error: undefined is not a function (near '...(0 , _reactNavigation.TabNavigator)...') Which you can see here: Preview of some of the files: App.js import React from 'react'; import { Drawer } from './src/navigators'; export default class App extends React.Component { render() { return ( <Drawer /> ); } } navigators.js import React, { Component } from 'react'; import { StyleSheet, Text, View } from 'react-native'; // Navigators import { DrawerNavigator,

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