S.O.L.I.D五大原则之依赖倒置原则DIP – 深入理解JavaScript系列 22

英文原文：http://freshbrewedcode.com/derekgreer/2012/01/22/solid-javascript-the-dependency-inversion-principle/

A. High-level modules should not depend on low-level modules.  Both should depend on abstractions.
   高层模块不应该依赖于低层模块，二者都应该依赖于抽象

B. Abstractions should not depend upon details.  Details should depend upon abstractions.
   抽象不应该依赖于细节，细节应该依赖于抽象

$.fn.trackMap = function(options) {
    var defaults = {
        /* defaults */
    };
    options = $.extend({}, defaults, options);

    var mapOptions = {
        center: new google.maps.LatLng(options.latitude,options.longitude),
        zoom: 12,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    },
        map = new google.maps.Map(this[0], mapOptions),
        pos = new google.maps.LatLng(options.latitude,options.longitude);

    var marker = new google.maps.Marker({
        position: pos,
        title: options.title,
        icon: options.icon
    });

    marker.setMap(map);

    options.feed.update(function(latitude, longitude) {
        marker.setMap(null);
        var newLatLng = new google.maps.LatLng(latitude, longitude);
        marker.position = newLatLng;
        marker.setMap(map);
        map.setCenter(newLatLng);
    });

    return this;
};

var updater = (function() {
    // private properties

    return {
        update: function(callback) {
            updateMap = callback;
        }
    };
})();

$("#map_canvas").trackMap({
    latitude: 35.044640193770725,
    longitude: -89.98193264007568,
    icon: 'http://bit.ly/zjnGDe',
    title: 'Tracking Number: 12345',
    feed: updater
});

$.fn.trackMap = function(options) {
    var defaults = {
        /* defaults */
    };

    options = $.extend({}, defaults, options);

    options.provider.showMap(
        this[0],
        options.latitude,
        options.longitude,
        options.icon,
        options.title);

    options.feed.update(function(latitude, longitude) {
        options.provider.updateMap(latitude, longitude);
    });

    return this;
};

$("#map_canvas").trackMap({
    latitude: 35.044640193770725,
    longitude: -89.98193264007568,
    icon: 'http://bit.ly/zjnGDe',
    title: 'Tracking Number: 12345',
    feed: updater,
    provider: trackMap.googleMapsProvider
});

trackMap.googleMapsProvider = (function() {
    var marker, map;

    return {
        showMap: function(element, latitude, longitude, icon, title) {
            var mapOptions = {
                center: new google.maps.LatLng(latitude, longitude),
                zoom: 12,
                mapTypeId: google.maps.MapTypeId.ROADMAP
            },
                pos = new google.maps.LatLng(latitude, longitude);

            map = new google.maps.Map(element, mapOptions);

            marker = new google.maps.Marker({
                position: pos,
                title: title,
                icon: icon
            });

            marker.setMap(map);
        },
        updateMap: function(latitude, longitude) {
            marker.setMap(null);
            var newLatLng = new google.maps.LatLng(latitude,longitude);
            marker.position = newLatLng;
            marker.setMap(map);
            map.setCenter(newLatLng);
        }
    };
})();