【JavaScript】各种手写题汇总复习

防抖

function throttle(fun, time) {
  let timer = null
  return () => {
    if (timer) {
      return
    }
    fun()
    timer = setTimeout(() => {
      timer = null
    }, time)
  }
}

节流

function debounce(fun, time) {
  let timer = null
  return () => {
    if (timer) {
      clearTimeout(timer)
    }
    timer = setTimeout(() => {
      fun()
    }, time)
  }
}

深拷贝

function deepClone(a, cache) {
  let res = undefined

  if (!cache) {
    cache = new Map()
  }

  if (a instanceof Object) {
    if (cache.get(a)) {
      return cache.get(a)
    }

    if (a instanceof Function) {
      if (a.prototype) {
        res = (...args) => {
          return a.call(this, ...args)
        }
      } else {
        res = (...args) => {
          return a.call(undefined, ...args)
        }
      }
    } else if (a instanceof Array) {
      res = []
    } else if (a instanceof Date) {
      res = new Date(a - 0)
    } else if (a instanceof RegExp) {
      res = new RegExp(a)
    } else {
      res = {}
    }

    cache.set(a, res)

    for (let k in a) {
      if (a.hasOwonProperty(k)) {
        res[k] = deepClone(a[k])
      }
    }

    return res
  } else {
    res = a
  }
}

手写 instanceof

function _instanceof(a, b) {
  if (typeof a !== 'object' || a === null) {
    return false
  }

  let proto = Object.getPrototypeOf(a)
  while (true) {
    if (proto === null) {
      return false
    }
    if (proto === b.prototype) {
      return true
    }
    proto = Object.getPrototypeOf(proto)
  }
}

手写 new

function _new(fn, ...args) {
  let o = Object.create(fn.prototype)
  let res = fn.apply(o, args)
  return typeof res === 'object' ? res : o
}

数组去重

// 1. set
function distDoWeight(arr) {
  return Array.from(new Set(arr))
}