编写可读性代码的艺术 #

const euclidean_norm = arr => {
  let retval = 0
  for (let i = 0 i < arr.length; i++) {
    retval += arr[i] * arr[i]
  }
  return Math.sqrt(retval)
}

someFunction({
  rotate: rotate_value
})

someFunction({
  route_cw: cw_value // 顺时针的弧度 anticlockwise/counterclockwise 逆时针
})

const numList = [1, 2, 3]
let sum = 0
for (let i = 0; i < array.length; i++) {
  sum += array[i];
}

for (i = 0; i < clubs.size(); i++) {
  for (j = 0; j < clubs[i].members.size(); j++) {
    for (k = 0; k < users.size(); k++) {
      // do something
    }
  }
}

for (club_i = 0; club_i < clubs.size(); club_i++) {
  for (member_i = 0; member_i < clubs[club_i].members.size(); member_i++) {
    for (user_i = 0; user_i < users.size(); user_i++) {
      // do something
    }
  }
}

const YYYYMMDD = '2023-03-23' // 这个变量，就能一眼推断出表示一个时间

const person = new Person()
const age = getAge()

const $allImages = $('img')

const div_ref = ref() // 表示引用一个 div
const com_ref = ref() // 表示引用一个 组件

const CART_TOO_BIG_LIMIT = 10 // 购物车最多10个物品
const MAX_ITEMS_IN_CART = 10 //  ✅  better

const str = 'abcd' // first = 0  last = 3 包含 d

const str = 'abcd' // start = 0  end = 3 不包含 d

// `is` + 形容词 或者直接形容词，具有某写属性
// `is` + 动词过去式，表示完成了某个都行 做完xxx
const isGood = true //
const good = true // ok 👌 但是不够明确
const isFinished = true
const sortable = false // ok
const isSorted = true // ok
const hidden = true // ok
// `is` + 名字 表示是不是某个东西
const isSon = true
const isRiver = true
// 名词 + `is` + 形容词
const orders_is_closed = true
// 也可以 `is` + 名词 + 形容词
const isOrdersClosed = true

// `has` + 名词 存在某些东西
const hasKey = true // 存在 key
const hasValue = true // 有值

// `should` + 动词原型 是否需要执行某个动作
const shouldCloseDB = true
// `can` + 动词 具备某种能力
const canEdit = true // 有编辑权限
// `enable` + 动词， 表示是否开启某种能力 是具备某个能力
const enableEdit = true
const enableRemove = true

function shouldRemoveBlank(remove) {
  //
}

const hasNoValue = arr.length === 0
// bad ❌
if (hasNoValue) {
  // do something
}
if (!hasNoValue) {
  // 不是没有值，产生双重否定
  // do something
}

const isAnyUserOffline = users.some(user => !user.isOnline)

if (isAnyUserOffline) {
  // 有人离线
}
// 使用 every
const isEveryUserOnLine = user.every(user => user.isOnline)
if (!isEveryUserOnLine) {
  // 不是每个人都在线
}

class StatisticCollector {
  addSample(x) {
    //
  }
  getMean() {
    // 遍历所有的 samples 返回平均数
  }
}

class StackKeeper {
  // A class for keeping track of a series of doubles
  add(d) {
    /*
        and methods for quick statistics about them.
       */
  }
  _minimum = 10
  /* how many so
     for
     */
  average() {}
}

// A class for keeping track of a series of doubles
// and methods for quick statistics about them.
class StackKeeper {
  add(d) {}
  _minimum = 10 // how many so for
  average() {}
}

class PerformanceTester {
  wifi = new TCPConnectionSimulator(
    500, /*kbps*/
    80, /*millisecs latency*/
    200, /*jitter*/
    1 /*packet loss  %*/ )
  t3_fiber =
    new TCPConnectionSimulator(
      45000, /*kbps*/
      10, /*millisecs latency*/
      0, /*jitter*/
      0 /*packet loss  %*/
    )
  cell = new TCPConnectionSimulator(
    100, /*kbps*/
    400, /*millisecs latency*/
    250, /*jitter*/
    5 /*packet loss  %*/
  )
}

class PerformanceTester {
  // new TCPConnectionSimulator(throughput,latency,jitter,packet_loss)
  //                               [kbps]    [ms]   [ms]   [percent]
  wifi = new TCPConnectionSimulator(500, 80, 200, 1)
  t3_fiber = new TCPConnectionSimulator(45000, 10, 0, 0)
  cell = new TCPConnectionSimulator(100, 400, 250, 5)
}

checkFullName('Doug Adams', 'Mr. Douglas Adams', '')
checkFullName(' Jake Brown', 'Mr. Jake Brown III', '')
checkFullName('No such Guy', '', 'no match found')
checkFullName('John', '', 'more than one results')

import hoverIntent from 'hoverintent'
import {
  ref
} from 'vue'
type InAndOut = {
  in ? : (target: HTMLElement) => void
  out ? : (target: HTMLElement) => void
}
const options = {
  in: target => undefined,
  out: target => undefined,
}
/**
 * 鼠标移入移出 hook，可设置鼠标停留时间。
 * 为何不使用 hover 事件：hover 事件瞬间触发，不能设置停留时间
 * @param target 目标元素
 * @param inAndOut 移入移除回调
 * @param inAndOut.in 移入回调
 * @param inAndOut.out 移出回调
 * @param updateTarget 是否更新 hover 的目标元素
 * @param opts hoverIntent配置
 * @link https://www.npmjs.com/package/hoverintent
 */
function useHover(inAndOut: InAndOut = options, updateTarget = false, opts = undefined) {
  const isHover = ref(false)
  const target = ref(null)
  watch(
    target,
    (target, oldTarget) => {
      if (target && target !== oldTarget) {
        detectHover(target)
      }
    }, {
      flush: 'post'
    }
  )

  function detectHover(target) {
    const _target = isRef(target) ? target.value : target
    if (!_target) return
    const {
      in: inTarget, out
    } = inAndOut
    opts &&
      hoverIntent(
        _target,
        () => {
          inTarget?.(_target)
          isHover.value = true
        },
        () => {
          out?.(_target)
          isHover.value = false
        }
      ).options(opts) !opts &&
      hoverIntent(
        _target,
        () => {
          inTarget?.(_target)
          isHover.value = true
        },
        () => {
          out?.(_target)
          isHover.value = false
        }
      )
  }
  return {
    isHover,
    setHoverTarget: ele => {
      if (!updateTarget && target.value) return
      target.value = ele
    },
  }
}
export {
  useHover
}

function useHover(inAndOut: InAndOut = options, updateTarget = false, opts = undefined) {
  const isHover = ref(false)
  const target = ref(null)
  watch(
    target,
    (target, oldTarget) => {
      if (target && target !== oldTarget) {
        detectHover(target)
      }
    }, {
      flush: 'post'
    }
  )
  return {
    isHover,
    setHoverTarget: ele => {
      if (!updateTarget && target.value) return
      target.value = ele
    },
  }

  function detectHover(target) {
    const _target = isRef(target) ? target.value : target
    if (!_target) return
    const {
      in: inTarget, out
    } = inAndOut
    opts &&
      hoverIntent(
        _target,
        () => {
          inTarget?.(_target)
          isHover.value = true
        },
        () => {
          out?.(_target)
          isHover.value = false
        }
      ).options(opts) !opts &&
      hoverIntent(
        _target,
        () => {
          inTarget?.(_target)
          isHover.value = true
        },
        () => {
          out?.(_target)
          isHover.value = false
        }
      )
  }
}

// as long as it is >= 2 * num_processors, its enough.
const MUN_THREADS = 8

const SECONDS_1DAY = 24 * 60 * 60;

if (length > 10) {
  //
}

if (10 < length) {
  //
}

let a = 1
if(a=1){ // ❌ 当 不小心把 == 写成 =，程序不报错
  // do something
}

let b = '123'
if('12' == b){ // 当 不小心把 == 写成 =， 程序报错
  // do something
}

if (a === b) {
  //  do a
} else {
  // do b
}

if (a !== b) {
  // do b
} else {
  // do a
}

const greet = ({
  firstName,
  lastName
}) => {
  if (firstName === undefined || lastName === undefined) {
    throw new Error("Invalid user");
  }
  return `Hello, ${firstName} ${lastName}`
}

if (e.rainMetrics && JSON.stringify(e.rainMetrics) !== '{}') {
  let arr = Object.getOwnPropertyNames(e.rainMetrics)
  if (arr.length !== 0) {
    if (e.rainPeriod && e.rainPeriod.length > 0) {
      e.rainPeriod.map(field => {
        if (e.rainMetrics[field].length > 0) {
          let oneObj, twoObj
          e.rainMetrics[field].forEach(b => {
            if (b.warnName === '准备转移') {
              twoObj = assign({}, oneObj, {
                intv: field,
                warnName: b.warnName,
                warnGradeId: b.warnGradeId,
                period: b.period,
                crp: b.crp,
              })
              tetList.push(twoObj)
            }
            if (b.warnName === '立即转移') {
              oneObj = assign({}, b, {
                intv: field,
                warnName: b.warnName,
                warnGradeId: b.warnGradeId,
                period: b.period,
                crp: b.crp,
              })
              tetList.push(oneObj)
            }
          })
        }
      })
    }
    tetList.forEach(v => {
      if (v.warnName === '准备转移') {
        threeObj['prepareTime' + v.period] = v.crp
      }
      if (v.warnName === '立即转移') {
        threeObj['immediatelyTime' + v.period] = v.crp
      }
    })
  }
}

if (user_result === 'SUCCESS') {
  if (permission_result !== 'SUCCESS') {
    reply.WriteErrors('error reading permission.')
    reply.Done()
    return
  }
  reply.WriteErrors('')
} else {
  reply.WriteErrors(user_result)
}
reply.Done()

if (user_result !== 'SUCCESS') {
  reply.WriteErrors(user_result)
  reply.Done()
  return
}
if (permission_result !== 'SUCCESS') {
  reply.WriteErrors('error reading permission.')
  reply.Done()
  return
}
reply.WriteErrors('')
reply.Done()

async function getBook(params) {
  const {
    id
  } = params;
  if (id) { // not an empty string
    const idAsInt = parseInt(id);
    if (!isNaN(idAsInt)) { // is it a number?
      const book = await findBook(idAsInt);
      return Response.ok(JSON.stringify(book));
    } else {
      throw Error("Id must be numeric");
    }
  } else {
    throw Error("Id must be present");
  }
}

async function getBook(params) {
  const {
    id
  } = params;
  if (!id) {
    throw Error("Id must be present");
  }

  const idAsInt = parseInt(id);
  if (Number.isNaN(idAsInt)) {
    throw Error("Id must be numeric");
  }

  const book = await findBook(idAsInt);
  return Response.ok(JSON.stringify(book));
}