function throttle(fn, time) {
    let pre = 0;
    let timer = null;
    return function(...args) {
        if(Date.now() - pre > time) {
            clearTimeout(timer);
            timer = null;
            pre = Date.now();
            fn.apply(this, args);
        } else if(!timer) {
            timer = setTimeout(() => {
                fn.apply(this, args);
            })
        }
    }
}