ArrayPrototype

Array API

//join
Array.prototype.join = function(char){
  let result = this[0] || ''
  let length = this.length
  for(let i=0;i<length;i++){
    result += char + this[i]
  }
  return result
}

//slice
Array.prototype.slice = function(begin,end){
  let result = this[0] || ''
  begin = begin || 0
  end = end || thsi.length
  for(let i = begin;i<end;i++){
    result.push(this[i])
  }
  return result
}

//sort
Array.prototype.sort = function(fn){
  fn = fn || (a,b)=>a-b
  let roundCount = this.length -1
  for(let i=0;i<roundCount;i++){
    for(let k=i+1;k<this.length;k++){
      if(fn.call(null,this[k],this[i])<0){
      [this[i],this[k]] = [this[k],this[i]]
      }
    }
  }
}

//forEach
Array.prototype.forEach = function(fn){
  for(let i=0;i<this.length;i++){
    if(i in this){
      fn.call(undefined,this[i],i this)
    }
  }
}

//map
Array.prototype.map = function(fn){
  let result = []
  for(let i=0;i<this.length;i++){
    if(i in this){
      result[i] = fn.call(undefined,this[i],i this)
    }
  }
  rturn result
}

//filter
Array.prototype.filter = function(fn){
  let result = []
  for(let i=0;i<this.length;i++){
    if(i in this){
      if(fn.call(undefined,this[i],i,this)){
      result.push(this[i])
      }
    }
  }
  return result
}

//reduce
Array.prototype.reduce = function(fn,init){
  let result = init
  for(let i=0;i<this.length;i++){
    if(i in this){
      result = fn.call(undefined,result,this[i],i,this)
    }
  }
  return result
}

array2 = array.map(v => v+1)

array2 = array.reduce((result,v)=>{
  result.push(v+1)
  return result
},[])


array2 = array.filter(v => v%2 === 0)

array3 = array.reduce((result,v)=>{
  if(v%2 === 0){
    result.push(v)
  }
  return result
},[])

函数节流

多长时间内 只执行一次
技能有cd 如果你一秒内用了一次 那你只能一秒后再用

fn2 = throttle(fn,time){
let cd = false
return function(){
    if(cd) {return}
    fn.call()
    cd = true
    setTimeout(()={cd = false},time)
  }
}

函数防抖

等多长时间不说话 我就去行动

我不想那么快的去做这件事情 我希望你把话说完了我再去做
我不想用户每次滚动都要去做这件事情 我希望用户停下来了 我再去做这件事情
我不想用户每次输入一个汉字我都要去问后台 我等用户停止输入了 我再去

debounce = function(fn,time){
  let timer = undefined
  return function(){
    if(timer !== undefined){
    window.clearTimeout(timer)
    }
    timer = setTimeout(()=>{
      fn.call()
    },time)
  }
}
fn  = function(){
  console.log(1)
}
fn2 = debounce(fn,10000)