在真实的软件开发过程中,无论使用何种编程开发语言,都不可避免的会遇到代码重复的问题。如何处理重复的问题,可以选择情怀(手动再敲一遍),也可以选择 Copy-to-Copy ,或者选择代码生成器。正如在之前的文章  我的写作工具链 中,我介绍过一种 Blog 生成器 hexo ,可以将 Markdown 格式的内容自动生成方便发布的 HTML 格式。本文将还原 hexo 的运行原理,为解决类似问题提供一些参考思路。
  这里输入引用文本示例:通过 Markdown 文件声明模板(源代码),通过脚本生成 HTML 文件(目标代码),并预览代码生成效果。
 
 Step 1: 准备环境 (dependencies)
 开发语言 Node.js, 一个能够运行 JavaScript 的开放源代码、跨平台运行环境。
  - npm init — 初始化 root 目录
- npm i -s live-server — 该模块支持本示例生成静态 HTML 站点,提供热部署能力
- npm i -s nodemon — 该模块支持当文件变化自动执行重构任务
- npm i -s concurrently — 该模块支持支持并发执行任务、脚本(scripts/tasks)
- npm i -s markdown-it — 该模块提供 Markdown 文件解析器
mkdir project-generator mkdir project-generator/pages mkdir project-generator/pages_meta mkdir project-generator/js mkdir project-generator/css mkdir project-generator/images mkdir project-generator/build_scripts mkdir project-generator/build  cd project-generator npm init  npm i -s concurrently npm i -s fs npm i -s fs-extra npm i -s markdown-it npm i -s live-server  npm i -s nodemon 
 
 Step 2: 准备元数据
 例如:pages/index.md
 # Home page  Hello world!  [Link to another page](./other.html)  
 例如:pages_meta/index.json 用于存储一些需要的元数据(参数、固定内容等),JSON 文件格式方便后面调用。
 {   "lang": "en",   "title": "Index",   "stylesheets": ["./css/style.css"],   "scripts": ["./js/main.js"],   "charset": "utf-8",   "description": "This is a page",   "keywords": "page, sample",   "author": "None",   "favicon": "./images/favicon.png",   "viewport": "width=device-width, initial-scale=1",   "extra": [] } 
 Step 3: 编写模板和构建脚本(template & build Script)
 代码生成器中需要定制开发的部分包括 builder.js 和 pages_template.js。build.js 相当于 main 函数,控制入口和流程,加载资源数据、调用 generator 任务,与 Makefile 和 Ant.xml 非常类似。pages_template.js 依赖的组件是 markdown-it ,负责将 Markdown 源文件转换输出成 HTML 文件。builder.js 将 pages_template.js 视为一个模块引用:pageTemplate.generatePage(pageContent, metaData)) 因此可以根据需要定制多个不同的 XXX_template.js 或者在每个 template.js 中定义其它函数。
 builder.js
 var pageTemplate = require('./page_template');  // All paths are relative to package.json. var pagesPath = './pages'; var pagesMetaPath = './pages_meta'; var copyFolders = ['./images', './css', './js']; var outputPath = './build';  // Clean console.log('Cleaning previous build...'); for (var file of fs.readdirSync(outputPath)){     fs.removeSync(path.join(outputPath, file)); }  //Loading console.log('Loading pages metadata...');   for(var pageMeta of fs.readdirSync(pagesMetaPath)){     pagesMeta[pageMeta] = fs.readFileSync(path.join(pagesMetaPath,pageMeta),'utf8');   } }  // Generate console.log('Generating pages...'); for(var page of Object.entries(pages)) {     var pageName = page[0].slice(0, page[0].lastIndexOf('.'));     var metaData = pagesMeta.hasOwnProperty(pageName+'.json')       ? JSON.parse(pagesMeta[pageName+'.json'])       : {};     metaData.title = metaData.title || pageName;     var pageContent = page[1];     fs.writeFileSync(       path.join(outputPath,pageName+'.html'),       pageTemplate.generatePage(pageContent, metaData));   } }  // Copy console.log('Copying folders...');   for(var copyFolder of copyFolders){     fs.copySync(copyFolder, path.join(outputPath,copyFolder));   }  
 pages_template.js
 var md = require('markdown-it')();  module.exports = {   generatePage: function(pageContent,pageMeta){     return`<!DOCTYPE html> <html lang="${pageMeta.lang || this.defaultMeta.lang}">   <head>     <title>${pageMeta.title || this.defaultMeta.title}</title>     <meta charset="${pageMeta.charset || this.defaultMeta.charset}">     <meta name="description" content="${pageMeta.description || this.defaultMeta.description}">     <meta name="keywords" content="${pageMeta.keywords || this.defaultMeta.keywords}">     <meta name="author" content="${pageMeta.author || this.defaultMeta.author}"> </head> <body>   ${md.render(pageContent)} </body> </html>     `;   } } 
 Step 4: 优化任务脚本
 在 Step 1 步骤中,npm init 创建了一个文件:package.json,我们可以定义其中的 “scripts” , 执行 npm run start 将默认在 1080 端口开启 Web 服务。
 
 {   "name": "coffee",   "version": "1.0.0",   "description": "beyond my coffee",   "main": "index.js",   "scripts": {       "build-pages": "node ./build_scripts/builder.js",     "start": "concurrently --kill-others \"nodemon -e js,json,css,md -i build -x \\\"npm run build-pages\\\"\" \"live-server ./build\""   },   "author": "@RiboseYim" } 
 $ npm run build-pages  > coffee@1.0.0 build-pages /generator-code > node ./build_scripts/builder.js  Cleaning previous build... Loading pages... Loading pages metadata... Generating pages... Copying folders... Done!  $ npm run start  > coffee@1.0.0 start /Users/yanrui/project/generator-code > concurrently --kill-others "nodemon -e js,json,css,md -i build -x \"npm run build-pages\"" "live-server ./build"  [0] [nodemon] 1.14.1 [0] [nodemon] to restart at any time, enter `rs` [0] [nodemon] watching: *.* [0] [nodemon] starting `npm run build-pages` [1] Serving "./build" at http://127.0.0.1:8080 [1] Ready for changes [1] GET /js/main.js 404 42.133 ms - 23 [1] GET /js/main.js 404 12.204 ms - 23 [0] [0] > coffee@1.0.0 build-pages /Users/yanrui/project/generator-code [0] > node ./build_scripts/builder.js [0] [0] Cleaning previous build... [0] Loading pages... [0] Loading pages metadata... [0] Generating pages... [0] Copying folders... [0] Done! [0] [nodemon] clean exit - waiting for changes before restart [1] Change detected build/index.html [1] Change detected build/images 
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