node.js cookie-parser 中间件介绍

var cookie = require('cookie');
var parse = require('./lib/parse');

var hdr = cookie.serialize('foo', 'bar');    // hdr = 'foo=bar';

var cookies = cookie.parse('foo=bar; cat=meow; dog=ruff'); // cookies = { foo: 'bar', cat: 'meow', dog: 'ruff' };

exports = module.exports = function cookieParser(secret, options){
  return function cookieParser(req, res, next) {  // 从请求中得到req,res对象
    if (req.cookies) return next();  // 如果已经有cookie对象，则退出中间件继续运行
    var cookies = req.headers.cookie; // 从headers中取cookie
 
    req.secret = secret;                     // 如果有传入secret,则设置到req对象
    req.cookies = Object.create(null);       // 创建空对象给req.cookies
    req.signedCookies = Object.create(null); // 创建空对象给req.signedCookies
 
    // no cookies
    if (!cookies) {   // 如果没有从headers得到cookies
      return next();  // 退出中间件继续运行
    }
 
    req.cookies = cookie.parse(cookies, options);  // 调用cookie的parse方便把cookie字符串转成cookies对象。
 
    // parse signed cookies
    if (secret) {                                 // 如果设置了secret，则使用 parse的2个方法，把cookie签名。
      req.signedCookies = parse.signedCookies(req.cookies, secret);
      req.signedCookies = parse.JSONCookies(req.signedCookies);
    }
 
    // parse JSON cookies
    req.cookies = parse.JSONCookies(req.cookies); // 把req.cookies对象转化
 
    next();
  };
};