防抖和节流

防抖
function debounce(fn,delay){
let t=null
    return function(){
        if(t===null){
        clearTimeout(t)
        } 
       t=setTimeout(()=>{
            fn()
        },delay)
        
    }
}
节流
function throttle(fn,delay){
    let flag=true
    return function(){
        if(flag){
            setTimeout(()=>{
                fn()
                flag=true
            },delay)
        }
        flag=false
    }
}