Take you to thoroughly understand the throttling and anti-shake in JS

First of all, throttling and anti-shake are used to continuously trigger events , such as the onscroll event. If you do not set throttling and anti-shake, when you bind the onscroll event and set the event processing function, you will execute more than n when you slide the scroll wheel. The second event processing function causes performance loss. Throttling and anti-shake are sometimes applied to the input keydown event. Choose throttling or anti-shake according to the specific situation.

Let me briefly explain the concepts of throttling and anti-shake.

• Throttling : When you keep triggering an event, execute the code you want to execute at regular intervals. (In order to prevent frequent triggering of events and execute code n times)

• Anti-shake : The event processing function is executed only once the event is not triggered in a fixed time interval after the trigger event is stopped. ( That is, when you continue to trigger an event, only the last code is executed )
  (If the event is triggered again within a fixed time interval, the time will be recalculated.)

• Throttling code

   var flag = true   //节流阀默认为true

   window.onscroll = function () {
    
         //触发事件后代码执行第一次
     if (flag === false) return     // 节流阀闭合则不执行

     flag = false // 来到这里即开关打开状态，现在关掉开关以免重复执行

     console.log('执行一次')
     setTimeout(() => {
    
      //为防止频繁触发，用延迟器来设置时间间隔
       flag = true     //0.5秒后打开开关
     }, 500)  //若事件被极频繁触发，也能保证至少等待0.5秒再执行下一次
										         //的事件处理函数
   }

• Anti-shake code

    var timer = null    //准备一个timer变量来操作定时器
    
    window.onscroll = function () {
    
      
      clearInterval(timer)   //触发事件就清除掉已有定时器
      					//保证了一定时间间隔内只执行一次事件处理函数
						//而这个时间间隔就是下边延时器的500ms
      timer = setTimeout(() => {
    
       //设置延时器
        console.log('触发')    
      }, 500)          //0.5秒内不触发该事件，则执行一次延时器内代码
    }