let lastTime=''

let code=''

let timer=null

document.addEventListener('keydown',(e)=>{

letthisTime=newDate().getTime() if(!lastTime){ lastTime=thisTime code=e.key }else{ if(thisTime-lastTime>10){ code='' lastTime='' }else{ code+=e.key lastTime=thisTime } } if(timer){ clearTimeout(timer) } timer=setTimeout(()=>{ if(code.length>3){ result=code 　　　console.log(result) } lastTime='' code='' },20)

})