前言

使用mock可以让前端不在局限于后端接口，在规定好文档格式后甚至能一次性开发完整个前端接口，大大节省了对接时间，可以说是当前前端必备的技能之一了。最近做新项目，重新搭建了下框架，想着写一篇mock的配置文章，让大家共同进步。

---

一、npm下载插件

npm install mockjs --save-dev

二、创建mock文件夹

1.在跟目录(src目录同级)下创建mock文件夹

2.mock文件夹下新建index.js文件

import Mock from 'mockjs'
import { param2Obj } from '../src/utils'

import user from './user'

const mocks = [
  ...user
]

// for front mock
// please use it cautiously, it will redefine XMLHttpRequest,
// which will cause many of your third-party libraries to be invalidated(like progress event).
export function mockXHR() {
  // mock patch
  // https://github.com/nuysoft/Mock/issues/300
  Mock.XHR.prototype.proxy_send = Mock.XHR.prototype.send
  Mock.XHR.prototype.send = function() {
    if (this.custom.xhr) {
      this.custom.xhr.withCredentials = this.withCredentials || false

      if (this.responseType) {
        this.custom.xhr.responseType = this.responseType
      }
    }
    this.proxy_send(...arguments)
  }

  function XHR2ExpressReqWrap(respond) {
    return function(options) {
      let result = null
      if (respond instanceof Function) {
        const { body, type, url } = options
        // https://expressjs.com/en/4x/api.html#req
        result = respond({
          method: type,
          body: JSON.parse(body),
          query: param2Obj(url)
        })
      } else {
        result = respond
      }
      return Mock.mock(result)
    }
  }

  for (const i of mocks) {
    Mock.mock(new RegExp(i.url), i.type || 'get', XHR2ExpressReqWrap(i.response))
  }
}

// for mock server
const responseFake = (url, type, respond) => {
  return {
    url: new RegExp(`${process.env.VUE_APP_BASE_API}${url}`),
    type: type || 'get',
    response(req, res) {
      console.log('request invoke:' + req.path)
      res.json(Mock.mock(respond instanceof Function ? respond(req, res) : respond))
    }
  }
}

export default mocks.map(route => {
  return responseFake(route.url, route.type, route.response)
})

// '../src/utils'
export function param2Obj(url) {
  const search = url.split('?')[1]
  if (!search) {
    return {}
  }
  return JSON.parse(
    '{"' +
      decodeURIComponent(search)
        .replace(/"/g, '\\"')
        .replace(/&/g, '","')
        .replace(/=/g, '":"')
        .replace(/\+/g, ' ') +
      '"}'
  )
}

 3.mock文件夹下新建mock-server.js文件

const chokidar = require('chokidar')
const bodyParser = require('body-parser')
const chalk = require('chalk')
const path = require('path')

const mockDir = path.join(process.cwd(), 'mock')

function registerRoutes(app) {
  let mockLastIndex
  const { default: mocks } = require('./index.js')
  for (const mock of mocks) {
    app[mock.type](mock.url, mock.response)
    mockLastIndex = app._router.stack.length
  }
  const mockRoutesLength = Object.keys(mocks).length
  return {
    mockRoutesLength: mockRoutesLength,
    mockStartIndex: mockLastIndex - mockRoutesLength
  }
}

function unregisterRoutes() {
  Object.keys(require.cache).forEach(i => {
    if (i.includes(mockDir)) {
      delete require.cache[require.resolve(i)]
    }
  })
}

module.exports = app => {
  // es6 polyfill
  require('@babel/register')

  // parse app.body
  // https://expressjs.com/en/4x/api.html#req.body
  app.use(bodyParser.json())
  app.use(bodyParser.urlencoded({
    extended: true
  }))

  const mockRoutes = registerRoutes(app)
  var mockRoutesLength = mockRoutes.mockRoutesLength
  var mockStartIndex = mockRoutes.mockStartIndex

  // watch files, hot reload mock server
  chokidar.watch(mockDir, {
    ignored: /mock-server/,
    ignoreInitial: true
  }).on('all', (event, path) => {
    if (event === 'change' || event === 'add') {
      try {
        // remove mock routes stack
        app._router.stack.splice(mockStartIndex, mockRoutesLength)

        // clear routes cache
        unregisterRoutes()

        const mockRoutes = registerRoutes(app)
        mockRoutesLength = mockRoutes.mockRoutesLength
        mockStartIndex = mockRoutes.mockStartIndex

        console.log(chalk.magentaBright(`\n > Mock Server hot reload success! changed  ${path}`))
      } catch (error) {
        console.log(chalk.redBright(error))
      }
    }
  })
}

4.mock文件夹下新建user.js文件

也就是在index.js中引入的模拟接口文件，这里已登陆接口为例

const tokens = {
  admin: {
    token: 'admin-token'
  },
  editor: {
    token: 'editor-token'
  }
}

export default [
  // user login
  {
    url: '/user/login',
    type: 'post',
    response: config => {
      const { username } = config.body
      const token = tokens[username]

      // mock error
      if (!token) {
        return {
          code: 60204,
          message: 'Account and password are incorrect.'
        }
      }

      return {
        code: 20000,
        data: token
      }
    }
  }
]

5.在main.js中引入

if (process.env.NODE_ENV === 'production') {
  const {
    mockXHR
  } = require('../mock')
  mockXHR()
}

 6.最后一步，也是最容易忘记的一步，在vue.config.js中写入

// webpack-devser@3.X的使用
module.exports = {
    devServer: {
        before: require('./mock/mock-server.js')
    }
}

// webpack-devser@4.X的使用
module.exports = {
    devServer: {
      onBeforeSetupMiddleware: (app, server, compiler) =>{
        require('./mock/mock-server.js')
      }
    }
}

---

总结

调用接口/user/login就就会执行mock的接口，返回我们写好的数据了。是不是很简单，大家快去试试吧。

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