function debounce(fn, time) {
    let timer
    return function(){
        var _that = this
        var arg = arguments
        // 高频率事件会在某个时间段内清除定时器，保证只执行最后一个
        if (timer) clearTimeout(timer)
        timer = setTimeout(() => {
            fn.call(_that, arg)
        }, time)
    }
}

function throttle(fn, time) {
    var timer
    return function() {
        var _this = this
        var arg = arguments
        if (!timer) {
            setTimeout(() => {
                timer = null
                fn.call(_that, arg)
            }, time)
        }
    }
}