---
title: 'React'
---


圖片來源：[Build Your Own React – Hacker Noon](https://hackernoon.com/build-your-own-react-48edb8ed350d)

---

## Component

組件化勢必是未來的前端開發不可或缺的一項技術，獨立封裝，彈性擴充，可移植性，測試等等…

---

直接來開個空白新專案吧

---

npm init -y


---

然後下載我個人 React 專案習慣用的工具

npm i -D @babel/core @babel/preset-env @babel/preset-react
npm i -D babel-eslint babel-loader clean-webpack-plugin
npm i -D eslint eslint-config-airbnb eslint-plugin-import
npm i -D eslint-plugin-jsx-a11y eslint-plugin-react
npm i -D html-webpack-plugin webpack webpack-cli
npm i -D webpack-dev-server webpack-merge

npm i classnames jss jss-preset-default normalize-jss
npm i react-jss prop-types react react-dom

---

這時我的 package.json 長這樣

{
  "name": "react-test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev": "webpack-dev-server --progress --colors --config ./config/webpack.dev.js",
    "build": "webpack --config ./config/webpack.prod.js",
    "lint": "eslint src/**"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@babel/core": "^7.4.4",
    "@babel/preset-env": "^7.4.4",
    "@babel/preset-react": "^7.0.0",
    "babel-eslint": "^10.0.1",
    "babel-loader": "^8.0.6",
    "clean-webpack-plugin": "^2.0.2",
    "eslint": "^5.16.0",
    "eslint-config-airbnb": "^17.1.0",
    "eslint-plugin-import": "^2.17.2",
    "eslint-plugin-jsx-a11y": "^6.2.1",
    "eslint-plugin-react": "^7.13.0",
    "html-webpack-plugin": "^3.2.0",
    "webpack": "^4.32.0",
    "webpack-cli": "^3.3.2",
    "webpack-dev-server": "^3.4.1"
  },
  "dependencies": {
    "classnames": "^2.2.6",
    "jss": "^9.8.7",
    "jss-preset-default": "^4.5.0",
    "normalize-jss": "^4.0.0",
    "prop-types": "^15.7.2",
    "react": "^16.8.6",
    "react-dom": "^16.8.6",
    "react-jss": "^8.6.1"
  }
}

---

配置 config/webpack.common.js

const path = require('path');

/* eslint import/no-extraneous-dependencies: ["error", {"devDependencies": true}] */

module.exports = {
  entry: [path.resolve(__dirname, '../src/index.jsx')],
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, '../dist/'),
    // publicPath: './',
  },
  module: {
    rules: [
      {
        test: /.js$/,
        use: [
          {
            loader: 'babel-loader',
            options: {
              presets: ['@babel/preset-env'],
            },
          },
        ],
      },
      {
        test: /.jsx$/,
        use: [
          {
            loader: 'babel-loader',
            options: {
              presets: ['@babel/preset-react', '@babel/preset-env'],
            },
          },
        ],
      },
    ],
  },
};

---

配置 config/webpack.dev.js

const webpack = require('webpack');
const merge = require('webpack-merge');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const common = require('./webpack.common');

/* eslint import/no-extraneous-dependencies: ["error", {"devDependencies": true}] */

module.exports = merge(common, {
  mode: 'development',
  devtool: 'cheap-module-eval-source-map',
  devServer: {
    open: true,
    historyApiFallback: true,
  },
  plugins: [
    new webpack.DefinePlugin({
      'process.env.NODE_ENV': JSON.stringify('development'),
    }),
    new HtmlWebpackPlugin({
      template: './index.html',
    }),
  ],
});

---

配置 config/webpack.prod.js

const webpack = require('webpack');
const merge = require('webpack-merge');
const CleanWebpackPlugin = require('clean-webpack-plugin');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const common = require('./webpack.common');

/* eslint import/no-extraneous-dependencies: ["error", {"devDependencies": true}] */

module.exports = merge(common, {
  mode: 'production',
  plugins: [
    new webpack.DefinePlugin({
      'process.env.NODE_ENV': JSON.stringify('production'),
    }),
    new CleanWebpackPlugin(),
    new HtmlWebpackPlugin({
      template: './index.html',
    }),
  ],
});

---

配置 babel.config.js 於根目錄

module.exports = {
  presets: [
    [
      '@babel/preset-env',
      { targets: { node: 'current' } },
    ],
    '@babel/preset-react',
  ],
};

---

配置 .eslintrc.js 於根目錄

module.exports = {
  parser: 'babel-eslint',
  parserOptions: {
    ecmaFeatures: {
      jsx: true,
    },
    ecmaVersion: 2018,
    sourceType: 'module',
  },
  env: {
    browser: true,
    es6: true,
    jest: true,
  },
  extends: [
    'plugin:react/recommended',
    'airbnb-base',
  ],
  plugins: [
    'react'
  ],
  rules: {
    'react/jsx-uses-react': 'error',
    'react/jsx-uses-vars': 'error',
    'linebreak-style': [
      'error',
      'windows',
    ],
  },
};

---

配置 index.html 於根目錄

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <meta name="viewport" content="minimum-scale=1, initial-scale=1, width=device-width, shrink-to-fit=no">
  <title></title>
</head>

<body>
  <div id="app"></div>
</body>

</html>

---

此時我的資料夾長這樣


---

到目前為止

都只是基本的配置環境

現在才要開始寫 React

---

剛剛在 webpack 設置裡的 entry 是 src/index.jsx

先從這個進入點開始定義

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src/index.jsx

import React from 'react';
import ReactDOM from 'react-dom';
import Root from './Root.jsx';

ReactDOM.render(<Root />, document.querySelector('#app'));

---

src/Root.jsx

import React from 'react';
import PropTypes from 'prop-types';
import withStyles from 'react-jss';
import jss from 'jss';
import preset from 'jss-preset-default';
import normalize from 'normalize-jss';

jss.setup(preset());
jss.createStyleSheet(normalize).attach();

const styles = {
  root: {
    fontFamily: 'system-ui, -apple-system, "Roboto", "Helvetica", "Arial", sans-serif',
  },
};

class Root extends React.Component {
  render() {
    const { classes } = this.props;

    return (
      <div className={classes.root}>
        我是 Root
      </div>
    );
  }
}

Root.propTypes = {
  classes: PropTypes.object.isRequired,
};

export default withStyles(styles)(Root);

---

設置完 jsx 後

就可以來執行看看 這兩個 jsx 的 render 結果

npm run dev

關於 dev 這個指令

// package.json
"scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev": "webpack-dev-server --progress --colors --config ./config/webpack.dev.js",
    "build": "webpack --config ./config/webpack.prod.js",
    "lint": "eslint src/**"
},

---


---

接下來我想要製作一個可以 alert 的 button

在點擊後會輸出我自己定義的 message

---

src/components/ButtonExecAlert.jsx

import React from 'react';
import PropTypes from 'prop-types';
import withStyles from 'react-jss';

/* eslint-disable class-methods-use-this */

const styles = {
  button: {
    width: 200,
    height: 100,
  },
};

class ButtonExecAlert extends React.Component {
  constructor(props) {
    super(props);
    this.handleClick = this.handleClick.bind(this);
  }

  handleClick() {
    alert(this.props.message);
  }

  render() {
    const { classes } = this.props;

    return (
      <button
        className={classes.button}
        onClick={this.handleClick}
      >
        點我有 alert
      </button>
    );
  }
}

ButtonExecAlert.propTypes = {
  classes: PropTypes.object.isRequired,
  message: PropTypes.string,
};

export default withStyles(styles)(ButtonExecAlert);

---

src/Root.jsx

import React from 'react';
import PropTypes from 'prop-types';
import withStyles from 'react-jss';
import jss from 'jss';
import preset from 'jss-preset-default';
import normalize from 'normalize-jss';
import ButtonExecAlert from './components/ButtonExecAlert.jsx';

...省略

class Root extends React.Component {
  render() {
    const { classes } = this.props;

    return (
      <div className={classes.root}>
        {/* 我是 Root  */}
        <ButtonExecAlert message="我的 alert" />
      </div>
    );
  }
}

---

此時就得到一個會 alert 然後 width height 有設定過的 button


---

回到 src/Root.jsx
我複製一個 ButtonExecAlert 的組件但是設定不一樣的 message

...省略

class Root extends React.Component {
  render() {
    const { classes } = this.props;

    return (
      <div className={classes.root}>
        <ButtonExecAlert message="我的 alert" />
        <ButtonExecAlert message="我的右邊的 alert" />
      </div>
    );
  }
}

---

此時畫面上就會有兩個自定義的組件

因為設定不同的 message 所以 alert 的結果會不同


---

此時我的資料夾長這樣


---

最後我要輸出成最一般的 html js (沒有 css 因為我用了 jss)

npm run build

關於 build 這個指令

// package.json
"scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev": "webpack-dev-server --progress --colors --config ./config/webpack.dev.js",
    "build": "webpack --config ./config/webpack.prod.js",
    "lint": "eslint src/**"
},

---

輸入完 npm run build 後會打包出 dist 資料夾


---

直接執行 dist 內的 index.html


---

這邊只是很粗淺的展示了 React 的 component

React 的生態還有非常非常多東西

不過這次只是打算快速介紹，所以就這樣

---

###### tags: `前端2`

下一章： [Material-UI](https://hackmd.io/p/Sy33TZ7nN#/)