开源（debounce）和节流（throttle）

学习：

function debounce(fn, time) {
    var settime = null
    
    return function() {
        if(settime !== null){
            clearTimeout(settime)
        }
        settime = setTimeout(fn, time)
    }
}

function handle() {
    console.log(Math.random())
}

window.addEventListener('scroll', debounce(handle, 1000))

以上是开源，滑动结束后一秒才会调用handle

function throttle(fn, time) {
    var pre = Date.now()
    
    return function() {
        var context = this
        var args = arguments
        var now = Date.now()
        if(now - pre >= time) {
            func.apply(context, args)
            pre = Date.now()
        }
    }
}

function handle() {
    console.log(Math.random())
}

window.addEventListener('scroll', throttle(handle, 1000))

以上是节流，持续一秒以上调用时，handle函数一秒调用一次