React学习笔记--程序调试

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。

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1. 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

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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

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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。