函数节流[throttle]

让函数保持在一个可接受的固定频率执行

let box=document.querySelector("#box")
let index=0;
function throttle(fn,interval=200,isStart=true){
  let timer=0;
  return function(...args){
  if(timer){ return }
  const _this=this;
  isStart&&fn.apply(_this,args);
  timer=setTimeout(()=>{
  (!isStart)&&fn.apply(_this,args);
  timer=0;
  },interval)
}
box.onmousemove=throttle(function(e){
index++;
console.log("move",index)
},1000,true);