SOURCE

// 防抖函数 延时执行
function debounce1(fn, wait) {
    let timer = null;
    return function () {
        let _this = this;
        let args = arguments;
        if (timer) {
            clearTimeout(timer);
            timer = null;
        }
        timer = setTimeout(() => {
            fn.apply(_this, args)
        }, wait)
    }
}
// 防抖函数 立即执行
function debounce2(fn, wait) {
    let timer;
    return function () {
        let _this = this;
        let args = arguments;
        if (timer) {
            clearTimeout(timer)
        }
        let applyNow = !timer;
        timer = setTimeout(() => {
            timer = null;
        }, wait)
        if (applyNow) {
            fn.apply(_this, args)
        }
    }
}

// 节流函数 时间戳版本
function throttle1(fn, delay) {
    let curTime = Date.now();
    return function () {
        let _this = this;
        let args = arguments;
        let now = Date.now();
        if (now - curTime >= delay) {
            curTime = Date.now();
            fn.apply(_this, args)
        }
    }
}
//节流函数 定时器版本
function throttle2(fn, wait) {
    let timer = null;
    return function () {
        let _this = this;
        let args = arguments;
        if (!timer) {
            timer = setTimeout(() => {
                timer = null;
                fn.apply(_this, args)
            }, wait)
        }
    }
}