React学习笔记

二程序调试

前面我们搭建好了React的基本开发环境，可以编写基本的React js程序了。完整的开发环境肯定包含调试器，怎么调试用React编写的JS程序呢？有浏览器，比如Firefox，Chrome，按F12，找到javaScript脚本，打断点，然后调试。这是调试JavaScript的基本环境，但是React由于使用了ES6的语法，在浏览器中经过Babel解析，或者在发布前就将React的代码编译成了ES5规范的JavaScript代码，我们调试时怎么能调试到自己的写的React代码呢？

前面我曾经提到使用Webpack打包发布React程序，那么我们能否借助Webpack来运行调试React程序呢？答案时肯定的。

首先我们在项目目录下安装相关的Babel，Webpack模块

npm init

npm install --save-dev webpack webpack-dev-server

npm install --save-dev react react-dom

npm install --save-dev babel-core babel-preset-react babel-preset-es2015 babel-loader babel-cli babel-plugin-transform-runtime

2.修改package.json

{

      "name": "demo1",

      "version": "1.0.0",

      "main": "webpack.config.js",

      "scripts": {

        "test": "echo \"Error: no test specified\" && exit 1"

      },

      "devDependencies": {

        "babel-cli": "^6.26.0",

        "babel-core": "^6.26.0",

        "babel-loader": "^6.4.1",

        "babel-plugin-transform-runtime": "^6.23.0",

        "babel-preset-es2015": "^6.24.1",

        "babel-preset-react": "^6.24.1",

        "react": "^15.6.2",

        "react-dom": "^15.6.2",

        "webpack": "^2.2.1",

        "webpack-dev-server": "^2.9.7"

      },

      "dependencies": {

        "react": "^15.6.2",

        "react-dom": "^15.6.2",

        "react-router-dom": "^4.2.2",

        "webpack-dev-server": "^2.4.1"

      },

      "presets": [

        "react"

      ],

      "author": "",

      "license": "ISC",

      "description": ""

}

3.项目下填加webpack.config.js

module.exports = {

    devtool: 'source-map',//这个配置很重要，告诉Webpack生成map.js，只有加入此配置才能在浏览器中真正调试React Js

    entry: './src/test.jsx',

    output: {

        filename: './lib/bundle.js'

    },

    module: {

        loaders: [

            {

                test: /\.js[x]?$/,

                exclude: /node_modules/,

                loader: 'babel-loader',

                query: {

                    presets: ['es2015', 'react']

                }

            }

        ]

    }

}

4..babelrc填加如下配置

{

    "presets": ["es2015","react"],

    "plugins": ["transform-runtime"],

    "comments": true

}

5.项目子目录src中创建test.jsx

import React from "react"

import ReactDOM from "react-dom"

var HelloMessage = React.createClass({

    render: function () {

        return <h1>Hello World！</h1>;

    }

});

ReactDOM.render(

    <HelloMessage />,

    document.getElementById('test')

);

6.创建index.htm，其中script直接引用webpack输出的js

<!DOCTYPE html>

<html>

    <body>

      <div id="test"></div>

      <script  src="../lib/bundle.js"></script>

    </body>

</html>

7.在console中的项目目录下运行webpack,可以看到在lib子目录下生成了bundle.js和bundle.map.js

PS D:\DEV\react\demo1> webpack

(node:9404) DeprecationWarning: loaderUtils.parseQuery() received a non-string value which can be problematic, see https://github.com/webpack/loader-utils/issues/56

parseQuery() will be replaced with getOptions() in the next major version of loader-utils.

Hash: 47d9ffef6066b3ac6378

Version: webpack 2.7.0

Time: 2131ms

              Asset    Size  Chunks                    Chunk Names

    ./lib/bundle.js  779 kB       0  [emitted]  [big]  main

./lib/bundle.js.map  942 kB       0  [emitted]         main

  [28] ./~/react/lib/React.js 4.96 kB {0} [built]

  [77] ./~/babel-runtime/helpers/typeof.js 1.07 kB {0} [built]

 [122] ./~/babel-runtime/core-js/object/get-prototype-of.js 104 bytes {0} [built]

 [123] ./~/babel-runtime/helpers/classCallCheck.js 208 bytes {0} [built]

 [124] ./~/babel-runtime/helpers/createClass.js 904 bytes {0} [built]

 [125] ./~/babel-runtime/helpers/inherits.js 1.11 kB {0} [built]

 [126] ./~/babel-runtime/helpers/possibleConstructorReturn.js 542 bytes {0} [built]

 [127] ./~/react-dom/index.js 59 bytes {0} [built]

 [128] ./~/react/react.js 56 bytes {0} [built]

 [129] ./src/test.jsx 5.21 kB {0} [built]

 [130] ./~/babel-runtime/core-js/object/create.js 94 bytes {0} [built]

 [131] ./~/babel-runtime/core-js/object/define-property.js 103 bytes {0} [built]

 [132] ./~/babel-runtime/core-js/object/set-prototype-of.js 104 bytes {0} [built]

 [137] ./~/babel-runtime/~/core-js/library/fn/object/get-prototype-of.js 125 bytes {0} [built]

 [199] ./~/react-dom/lib/ReactDOM.js 5.05 kB {0} [built]

    + 254 hidden modules

8.启动webpack-dev-server,访问http://localhost:8080就可以看到helloword了。

PS D:\DEV\react\demo1> webpack-dev-server --inline

Project is running at http://localhost:8080/

webpack output is served from /

(node:4340) DeprecationWarning: loaderUtils.parseQuery() received a non-string value which can be problematic, see https://github.com/webpack/loader-utils/issues/56

parseQuery() will be replaced with getOptions() in the next major version of loader-utils.

Hash: 64a0de3cefb7972eab47

Version: webpack 2.7.0

Time: 2449ms

              Asset     Size  Chunks                    Chunk Names

    ./lib/bundle.js   1.1 MB       0  [emitted]  [big]  main

./lib/bundle.js.map  1.32 MB       0  [emitted]         main

chunk    {0} ./lib/bundle.js, ./lib/bundle.js.map (main) 1.07 MB [entry] [rendered]

  [124] ./src/test.jsx 5.21 kB {0} [built]

  [125] (webpack)-dev-server/client?http://localhost:8080 7.95 kB {0} [built]

  [130] ./~/babel-runtime/core-js/object/get-prototype-of.js 104 bytes {0} [built]

  [134] ./~/babel-runtime/helpers/classCallCheck.js 208 bytes {0} [built]

  [135] ./~/babel-runtime/helpers/createClass.js 904 bytes {0} [built]

  [136] ./~/babel-runtime/helpers/inherits.js 1.11 kB {0} [built]

  [137] ./~/babel-runtime/helpers/possibleConstructorReturn.js 542 bytes {0} [built]

  [198] ./~/react-dom/index.js 59 bytes {0} [built]

  [282] ./~/react/react.js 56 bytes {0} [built]

  [284] ./~/strip-ansi/index.js 161 bytes {0} [built]

  [285] ./~/url/url.js 23.3 kB {0} [built]

  [287] (webpack)-dev-server/client/overlay.js 3.73 kB {0} [built]

  [290] (webpack)/hot nonrecursive ^\.\/log$ 160 bytes {0} [built]

  [291] (webpack)/hot/emitter.js 77 bytes {0} [built]

  [292] multi (webpack)-dev

9.打开firefox（本人使用firefox浏览器进行调试），在调试器左侧资源栏中可以找到webpack相关的资源，找到自己编写的test.jsx，打上断点，就可以像调试ES5一样调试自己写的React代码了。

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React学习笔记--程序调试

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二 程序调试

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