節流

function throttle(fn, delay) {
    let lastTime = 0;
    return function () {
        let nowTime = Date.now();
        if (nowTime - lastTime > delay) {
            fn().call(this);
            lastTime = nowTime;
        }
    }
}

防抖

function debounce(fn, delay) {
    var timer = null;
    return function () {
        clearTimeout(timer);
        timer = setTimeout(function () {
            fn.call(this);
        }, delay);
    }
}