玩转编程语言:基于Node.js构建自定义代码生成器

摘要

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。

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。

一、Hello Node.js

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
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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

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# 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。

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{
"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.jspages_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

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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

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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。

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{
"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"
}
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$ 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

Application

Hexo

Hexo Startup

Hexo Theme

Hexo Questions

  • Hexo g 失败【Uncaught SyntaxError: Invalid or unexpected token】:临时办法-复制到Editplus查看乱码

扩展阅读

参考文献

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