節(jié)流函數(shù)

 1         window.onscroll=throttle(function(){
 2             alert(1)
 3         },1000)
 4         function throttle(fn,delay) {
 5             let t=true;
 6             return function(){
 7                 if(t) {
 8                 setTimeout(()=>{
 9                     fn.call(this)
10                     t=true
11                 },delay)    
12                 }
13                 t=false
14             }
15         }