low版防抖节流

        function fd(delay, callback) {
            let timer = null;
            return function () {
                clearTimeout(timer)
                timer = setTimeout(() => {
                    callback();
                }, delay);
            }
        }
        function jl(delay, callback) {
            let time = Date.now();
            return function () {
                if (Date.now() - time > delay) {
                    callback();
                    time = Date.now();
                }
            }
        }
        // window.onscroll = fd(1000, () => {
        //     console.log('滚动')
        // })
        window.onscroll = jl(1000, () => {
            console.log('滚动')
        })