节流和防抖的实现

function debounce(fn, delay) {
    var timer;
    return function() {
        var that = this;
        var args = arguments;
        clearTimeout(timer);
        timer = setTimeout(function() {
            fn.apply(that, args);
        }, delay);
    }
}    

function throttle(fn, interval) {
    var previousTime = +new Date()


    return function () {
        var that = this
        var args = arguments
        var now = +new Date()
        if (now - previousTime >= interval) {
            previousTime = now
            fn.apply(that, args)
        }
    }
}                

function throttle(fn, interval) {
    var previousTime = +new Date()


    return function () {
        var that = this
        var args = arguments
        var now = +new Date()
        if (now - previousTime >= interval) {
            previousTime = now
            fn.apply(that, args)
        }
    }
}

function throttle(fn, interval) {
    var previousTime = +new Date()


    return function () {
        var that = this
        var args = arguments
        var now = +new Date()
        if (now - previousTime >= interval) {
        previousTime = now
        fn.apply(that, args)
        }
    }
}