JavaScript目录菜单滚动反显组件的实现

/*
 * 导航/菜单高亮组件
 * option
 *   nav 导航/菜单选择器
 *   content 内容模块选择器
 *   diffTop 距离顶部的误差值
 *   diffBottom 距离底部的误差值
 *   lightCls 高亮的class
 * 
 */
$.fn.navLight = function(option, callback) {
    option = option || {}
    var nav = option.nav || ‘[data-widget=nav]‘
    var content = option.content || ‘[data-widget=content]‘
    var diffTop = option.diffTop || 200
    var diffBottom = option.diffBottom || 500
    var lightCls = option.lightCls || ‘curr‘

    var $self = $(this)
    var $nav = $self.find(nav)
    var $content = $self.find(content)

    // 记录每个分类的位置
    var contentPosi = $content.map(function(idx, elem) {
        var $cont = $(elem)
        var top = $cont.offset().top
        var height = $cont.height()
        return {
            top: top-diffTop,
            bottom: top+diffBottom,
            jq: $cont
        }
    })

    var $win = $(window)
    var $doc = $(document)

    var handler = $.throttle(function(e) {
        var dTop = $doc.scrollTop()
        highLight(dTop)
    }, 100)
    
    function highLight(docTop) {
        contentPosi.each(function(idx, posi) {
            if (posi.top < docTop && posi.bottom > docTop) {
                $nav.removeClass(lightCls)
                $nav.eq(idx).addClass(lightCls)
                if (callback) {
                    callback($nav, $content)
                }
            }
        })
    }

    $win.scroll(handler)
};