[anti shake and throttling]

Anti shake of events

When a function executes too many times in a certain time , We need to reduce the frequency , If in 200ms The scrolling event is not triggered again within , Execute the function for so long If 220ms The scrolling event is triggered again in the , Then cancel the current timing . Restart the clock . Effect if a large number of scrolls are triggered in a short time, the function will only be executed once   . We can use the function /* * Parameters * fn： A function to be executed * delay： Delay time */ function debounce（fn,delay）{    // First create a variable to store a timer    var timer=null;    // The following line of code is closure    return function（）{        if（timer）{            clearTimeout（timer）       }        timer=setTimeout（fn,delay）   }     }

The throttling of events

function throttle(fn,delay){
    var valid=true;
    return function(){
        if(!valid){
            return valid=true
        }
     valid=false
     setTimeout(function(){
         fn();
         valid=true;
     },2000)
    }
}