正则表达式的x位数和只有一个连字符？(Regular expression for x number of digits and only one hyphen?)

 https://jsfiddle.net/9Luvrvc1/1/ 
 
 您可以使用相同的代码，在计数器功能处使用减号： 
 
$(document).ready(function() {
    var count;
    var interval;

    $(".ca-top").on('mouseover', function() {
        var div = $('.navbar-nav.categories');

        intervalDown = setInterval(function(){
            count = count || 1;
            var pos = div.scrollTop();
            div.scrollTop(pos + count);
        }, 10);
    }).click(function() {
        if (count < 6) {
             count = count+1;
        }
    }).on('mouseout', function() {
        // Uncomment this line if you want to reset the speed on out
        count = 0;
        clearInterval(intervalDown);
    });

    $(".ca-bottom").on('mouseover', function() {
        var div = $('.navbar-nav.categories');

        intervalUp = setInterval(function(){
            count = count || 1;
            var pos = div.scrollTop();
            div.scrollTop(pos - count);
        }, 10);
    }).click(function() {
        if (count > 6) {
             count = count-1;
        }
    }).on('mouseout', function() {
        // Uncomment this line if you want to reset the speed on out
        count = 0;
        clearInterval(intervalUp);
    });    

});
 
 但是，您可以尝试创建类似滚动（方向）的功能 - 这将使您的代码更短，更好阅读。 

https://jsfiddle.net/9Luvrvc1/1/
 
You can just use the same code, with a minus at the counter function:
 
$(document).ready(function() {
    var count;
    var interval;

    $(".ca-top").on('mouseover', function() {
        var div = $('.navbar-nav.categories');

        intervalDown = setInterval(function(){
            count = count || 1;
            var pos = div.scrollTop();
            div.scrollTop(pos + count);
        }, 10);
    }).click(function() {
        if (count < 6) {
             count = count+1;
        }
    }).on('mouseout', function() {
        // Uncomment this line if you want to reset the speed on out
        count = 0;
        clearInterval(intervalDown);
    });

    $(".ca-bottom").on('mouseover', function() {
        var div = $('.navbar-nav.categories');

        intervalUp = setInterval(function(){
            count = count || 1;
            var pos = div.scrollTop();
            div.scrollTop(pos - count);
        }, 10);
    }).click(function() {
        if (count > 6) {
             count = count-1;
        }
    }).on('mouseout', function() {
        // Uncomment this line if you want to reset the speed on out
        count = 0;
        clearInterval(intervalUp);
    });    

});
 
However you can try to make a function like scroll(direction) - which will make your code shorter and better to read.