防抖

防抖就是在持續(xù)調(diào)用中不會(huì)執(zhí)行，只有當(dāng)停止后一定時(shí)間才會(huì)執(zhí)行一次绍弟。主要作用場(chǎng)景：
1.search搜索聯(lián)想砂豌，用戶在不斷輸入值時(shí)，用防抖來(lái)節(jié)約請(qǐng)求資源
2.window觸發(fā)resize的時(shí)候煌寇，不斷的調(diào)整瀏覽器窗口大小會(huì)不斷的觸發(fā)這個(gè)事件，用防抖來(lái)讓其只觸發(fā)一次

//方法一：定時(shí)器
function debounce(fn,wait){
  let timer = null;
  function retimer(){
    if(timer){
     clearTimeout(timer);
    }
    timer = setTimeout(fn,wait)
  }
  return retimer;
}

//方法二：時(shí)間戳和定時(shí)器
function debounce(fn,wait){
  let timer,timeStamp=0;
  let context,args;
  let run = ()=>{
    timer = setTimeout(()=>{
      fn.apply(context,args)
    },wait)
  }
  let clean = ()=>{
    clearTimeout(timer)
  }
  return function(){
    content = this;
    args = arguments;
    let now = (new Date()).getTime();
    if(now-timeStamp < wait){
      clean();
      run();
    }else{
      run();
    }
    timeStamp = now;
  }
}

//方法三
function debounce(fn,wait){
  let timer,timeStamp=0;
  let context,args;
  let run = (timerInterval)=>{
    timer = setTimeout(()=>{
       let now = (new Date()).getTime();
       let interval = now - timeStamp;
       if(interval<timerInterval){
        timeStamp = now;
        run(wait-interval);
       }else{
        fn.apply(context,args);
        clearTimeout(timer);
        timer = null;
       }
    },timerInterval)
  }
  return function(){
    content = this;
    args = arguments;
    let now = (new Date()).getTime();
    timeStamp = now;
    if(!timer){
      run(wait);
    }
  }
}

方法的調(diào)用

<input id="input" >

function handler(){
    console.log('111111');
}
document.getElementById('input').addEventListener('keydown',debounce(handler,1000))
window.addEventListener('resize',debounce(handler,1000))

節(jié)流

防抖就是在一段時(shí)間內(nèi)持續(xù)調(diào)用逾雄，但只會(huì)執(zhí)行一次阀溶。
主要作用場(chǎng)景：
1.鼠標(biāo)不斷點(diǎn)擊觸發(fā)，mousedown(單位時(shí)間內(nèi)只觸發(fā)一次)
2.監(jiān)聽滾動(dòng)事件嘲驾，比如是否滑到底部自動(dòng)加載更多

//方法一
function throttle(fn,wait){
  let canRun = true;
  return function(){
    if(!canRun){
      return;
    }else{
      canRun = false;
      setTimeout(()=>{
        fn.apply(this,arguments);
        canRun = true;
      },wait);
    }
  }
}

//方法二
function throttle(fn,wait){
  let timer;
  let context,args;
  let run = ()=>{
    timer = setTimeout(()=>{
      fn.apply(content,args);
      clearTimeout(timer);
      timer = null;  
    },wait)
  }
  return function(){
    context = this;
    args = arguments;
    if(!timer){
      run();
    }
  }
}

//方法三
function(func, delay) {
    var timer = null; // 使用閉包淌哟，緩存變量
    var prev = Date.now(); // 最開始進(jìn)入滾動(dòng)的時(shí)間
    return function() {
      var context = this;   // this指向window
      var args = arguments;
      var now = Date.now();
      var remain = delay - (now - prev); // 剩余時(shí)間
      clearTimeout(timer);
      // 如果剩余時(shí)間小于0，就立刻執(zhí)行
      if (remain <= 0) {
        func.apply(context, args);
        prev = Date.now();
      } else {
        timer = setTimeout(func, remain);
      }
    }
  }

方法的調(diào)用

<div id="container"></div>

 function handler() {
      console.log('111111');
  }
document.getElementById('container').addEventListener('click', throttle(handler, 1000));