通過koajs的cookies方法設定cookie時，寫了中文的cookie值，一直失敗。程式碼如下:

this.cookies.set('test', '我是koajs')

報錯如下：

sent error argument value is invalid to the cloud
TypeError: argument value is invalid
    at new Cookie (/Users/zyy/github/fete/node_modules/cookies/lib/cookies.js:110:11)
    at Cookies.set (/Users/zyy/github/fete/node_modules/
 
cookies/lib/cookies.js:73:16)
    at Object.<anonymous> (/Users/zyy/github/fete/app.js:54:18)
    at next (native)
    at onFulfilled (/Users/zyy/github/fete/node_modules/co/index.js:65:19)
    at /Users/zyy/github/fete/node_modules/co/index.js:54:5
    at Object.co (/Users/zyy/github/fete/node_modules/co/index.js:50:10)
    at converted (/Users/
 
zyy/github/fete/node_modules/koa-convert/index.js:17:15)
    at dispatch (/Users/zyy/github/fete/node_modules/koa-compose/index.js:43:32)
    at next (/Users/zyy/github/fete/node_modules/koa-compose/index.js:44:18)
    at createGenerator (/Users/zyy/github/fete/node_modules/koa-convert/index.js:24:16)
    at next (native)
    at onFulfilled (/Users/
 
zyy/github/fete/node_modules/co/index.js:65:19)
    at /Users/zyy/github/fete/node_modules/co/index.js:54:5
    at Object.co (/Users/zyy/github/fete/node_modules/co/index.js:50:10)
    at Object.toPromise (/Users/zyy/github/fete/node_modules/co/index.js:118:63)

倒騰了半夜也沒找到方案，其實是http協議的Header頭有字元限制，下圖是stackoverflow的解答，http的header字符集支援US-ASCII子集的字符集，故設定中文是'utf8'時就會報上面錯誤。

故解決方案：
把字串轉成base64即可

this.cookies.set('test', new Buffer('我是koajs').toString('base64'))

base64轉到字串

new Buffer(str, 'base64').toString();//str是base64編碼的字串