什么是Markdown，就是一种标记语言，能够清楚快捷的输出所要的文本内容（格式上有增强效果），支持html。Github上的readme就是用markdown来实现。今天学习一下为Node.js上Express添加Markdown功能。Express 并不直接支持markdown语法，需要为项目添加markdown-js模块的依赖。

1.修改pacage.json

原版：

{
    "name": "application-name"
    , "version": "0.0.1"
    , "private": true
    , "dependencies": {
      "express": "2.4.6"
    , "jade": ">= 0.0.1"
  }
}

修改为：

{
    "name": "LazyBlog"
    , "version": "0.0.1"
    , "private": true
    , "dependencies": {
      "express": "2.4.6"
    , "jade": ">= 0.0.1"
    , "markdown-js": ">= 0.0.1"
  }
}

然后CMD进入LazyBlog目录，安装依赖：npm install

会在LazyBlog生成node_modules 目录，里边有

现在可以写代码了，打开app.js，导入markdown模块

var express = require('express')
  , routes = require('./routes')
  , markdown=require('markdown-js');

var app = module.exports = express.createServer();

然后给Express注册Markdown渲染器

app.configure('development', function(){
  app.use(express.errorHandler({ dumpExceptions: true, showStack: true }));
});

app.configure('production', function(){
  app.use(express.errorHandler());
});

app.register('.md',{
	compile:function(str,options){
		var html=markdown.makeHtml(str);
		return function(locals){
			return html.replace(/\{([^}]+)\}/g,function(_,name){
				return locals[name];
			});
		}
	}
});
// Routes

接着添加对markdown的路由（如果这些看起来对你很头大，那么先学学Express.js吧，上一篇文章有写过。如果不知道路由什么意思？那就先去学Node.js吧…）

app.get('/', routes.index);
//app.get('/md5/:string',routes.md5);
app.get('/markdown',function(req,res){
	res.render('index.md',{layout:false});
});

路由写好了，它指向index.md，用它来处理markdown语法文本，所以我们要去views目录建立一个index.md文件。

打开index.md ，现在可以写一写markdown标记的文本了，这里我把windows下markdownpad的欢迎界面内容搬过来了，你可以自己写点别的，比如

This is a demo page
===================
[Lazynight](http://lazynight.me \"Click\")

MarkdownPad欢迎界面

# Welcome to MarkdownPad #

**MarkdownPad** is a full-featured Markdown editor for Windows. 

## Full control over your documents ##

Want to make something **bold**? Press `Ctrl + B`.

How about *italic*? Press `Ctrl + I`.

> Write a quote with `Ctrl + Q`

No matter what you're working on, you'll have quick access to Markdown syntax with handy keyboard shortcuts and toolbar buttons.

## See your changes instantly with LivePreview ##

Don't guess if your [hyperlink syntax](http://markdownpad.com) is correct; LivePreview will show you exactly what your document looks like every time you press a key.

## Make it your own ##

Fonts, sizes, color schemes, and even the HTML stylesheets are 100% customizable so you can turn MarkdownPad into your ideal editor.

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