Knockout asynchronous templates

knockout.templates.js

(function(undefined) {
    "use strict";
    
    if (!ko.templates) {
        ko.templates = {};
    }
    
    if (!ko.templates_data) {
        ko.templates_data = {};
    }
    
    var StringTemplate = function(template) {
        this.template = template;
    }
    
    StringTemplate.prototype.data = function (key, value) {
        ko.templates_data[this.template] = ko.templates_data[this.template] || {};
        if (arguments.length == 1) {
            return ko.templates_data[this.template][key];
        }
        ko.templates_data[this.template][key] = value;
    }
    
    StringTemplate.prototype.text = function (value) {
        if (arguments.length == 0) {
            var template = ko.templates[this.template];
            if (template == null) {
                throw Error("Template not found : " + this.template);
            }
            return template;
        }
        ko.templates[this.template] = value;
    }
    
    ko.templateSources.stringTemplate = StringTemplate;
    
    var Engine = ko.nativeTemplateEngine.clone();
    
    Engine.prototype.makeTemplateSource = function (template, options, template_document, callback) {
        if (typeof template == "string") {
            if (typeof options == "object" && options.url) {
                if (ko.templates[template]) {
                    callback(new StringTemplate(template));
                } else {
                    $.get(options.url, function (template_data) {
                        $(template_data).find("script").addBack("script").each(function() {
                            ko.templates[$(this).attr("id")] = $(this).html();
                        });
                        callback(new StringTemplate(template));
                    });
                }
            } else {
                var element = template_document.getElementById(template);
                if (element) {
                    callback(new ko.templateSources.domElement(template));
                } else {
                    callback(new StringTemplate(template));
                }
            }
        } else if (typeof template == "object") {
            if (template.nodeType == 1 || template.nodeType == 8) {
                callback(new ko.templateSources.anonymousTemplate(template));
            } else {
                throw new Error("Unknown template type : " + template);
            }
        } else {
            throw new Error("Unknown template type : " + template);
        }
    }
    
    Engine.prototype.renderTemplate = function (template, binding_context, options, template_document, callback) {
        var self = this;
        this.makeTemplateSource(template, options, template_document, function (template_source) {
            self.renderTemplateSource(template_source, binding_context, options, callback);
        });
    }
    
    ko.setTemplateEngine(new Engine());
}) ();