A Node.js cookie module, a middleware based on express or my core.js module

Cookie.js

class Cookie {
  constructor(req, res) {
    this._cookie = []
    this._req = req
    this._res = res
    const cookie = req.headers.cookie
    const _hackHead = res.writeHead
    if(cookie) {
      const cook = cookie.split(';')
      cook.forEach((c) => {
        this._cookie.push(c.trim())
      })
    }
    req.cookie = this
    res.writeHead = (...args) => {
      res.setHeader('Set-Cookie', this._cookie)
      _hackHead.apply(res, args)
    }
  }
  
  parse() {
    if (this._req.headers.cookie){
      let cookies = {}
      this._req.headers.cookie.split(';').forEach((cookie) => {
        let parts = cookie.split('=')
        cookies[ parts[0].trim() ] = ( parts[1] || '').trim()
      })
      return cookies
    } else {
      return null
    }
  }
  
  set(k, v, opt={}) {
    let cookie = `${k}=${v}`
    const keys = Object.keys(opt)
    for( let i = 0; i < keys.length; i++ ) {
      const thisKey = keys[i]
      cookie += `;${thisKey}=${opt[thisKey]}`
    }
    this._cookie.push(cookie)
  }
  
  remove(k) {
    const regStr = '^' + k + '=[^;]+'
    const reg = new RegExp(regStr)
    for(let i = 0; i < this._cookie.length; i++) {
      const cook = this._cookie[i]
      if(reg.test(cook)) {
        this._cookie[i] = cook + ';expires=Thu, 01 Jan 1970 00:00:00 GMT'
      }
    }
  }
}

module.exports = Cookie

//to use
const Cookie = require('./lib/cookie')
const app = require('./lib/core')()
app.use('/', (req, res, next) => {
  new Cookie(req, res)
  next()
})

app.get('/', (req, res) => {
  req.cookie.set('user', 'mirone')
  res.end()
})

app.get('/update', (req, res) => {
  req.cookie.set('user', 'homura')
  res.writeHead(200, {'Content-Type': 'text/plain'})
  res.end()
})

app.get('/delete', (req, res) => {
  req.cookie.remove('user')
  res.writeHead(200, {'Content-Type': 'text/plain'})
  res.end()
})