Synchronizing scroll of two elements

textarea-synchronize-scroll.js

var scrollAreas = $('#content, .meltdown_preview');
    var textArea = $('#content');
    var previewArea = $('.meltdown_preview');
    var timer;

    var sync = function () {

        var percentage, x;

        if ($(this).attr('class') == 'meltdown_preview') {

            textArea.unbind("scroll");

            percentage = this.scrollTop / (this.scrollHeight - this.offsetHeight);

            x = percentage * (textArea.get(0).scrollHeight - textArea.get(0).offsetHeight);

            textArea.scrollTop(x);

            if (typeof(timer) !== 'undefined')
                clearTimeout(timer);

            timer = setTimeout(function () {
                textArea.scroll(sync)
            }, 200)

        } else {

            previewArea.unbind("scroll");

            percentage = this.scrollTop / (this.scrollHeight - this.offsetHeight);

            x = percentage * (previewArea.get(0).scrollHeight - previewArea.get(0).offsetHeight);

            previewArea.scrollTop(x);

            if (typeof(timer) !== 'undefined')
                clearTimeout(timer);

            timer = setTimeout(function () {
                previewArea.scroll(sync)
            }, 200)

        }

    }

    scrollAreas.on('scroll', sync);