What is the best way to incorporate custom KnockoutJS functions using RequireJS?

I am facing an issue with my View Model that utilizes a custom observableArray function for sorting. The error message I receive states: "...has no methods 'sortByProperty'".

How do I go about loading the handlers.js file to resolve this problem?

handlers.js:

define(['knockout'], function(ko) {
        'use strict';

        ko.observableArray.fn.sortByProperty = function (prop, order) {
            this.sort(function (obj1, obj2) {
                var result;
                if (obj1[prop] == obj2[prop])
                    result = 0;
                else if (obj1[prop] < obj2[prop])
                    result = -1;
                else
                    result = 1;

                return order === "desc" ? -result : result;
            });
        };

    });

viewmodel.js:

define([
        'knockout',
        'js/extends/handlers'
    ], function(ko) {
        'use strict';

        var LabelsModel = function() {
            var self = this;

            self.availableLabels = ko.observableArray();
            self.selectedLabel = ko.observable();
            self.sortBy = ko.observable(); // Field to sort by
            self.sortOrder = ko.observable(); // Sort order. asc or desc.

            // Returns the labels for the current page
            self.pagedRows = ko.computed(function() {
                // Sorting of labels
                return self.availableLabels.sortByProperty(self.sortBy(), self.sortOrder());
            });

        };

        return LabelsModel;

    });

Answer №1

Firstly, it's important to ensure that KnockoutJS is defined before loading the plugins and launching your application. This sequence of steps should ideally be followed when loading plugins for libraries. Below is an example of how you can achieve this:

require.config({
        paths: {
        jquery: 'libs/jquery-1.9.0.min',
        ko: 'libs/knockout-2.2.1.min'
    }
});

require(['jquery', 'ko'], 
    function($, ko) {
        // Make sure KO is in the global namespace ('this') 
        if (!this.ko) {
            this.ko = ko;
        };

        requirejs(['handlers'],
            function () { 
                require(['app'], 
                    function(App) { 
                        App.initialize(); 
                    }
                );
            }
        );
    }
);

Although I have simplified by including only JQuery and KnockoutJS, the basics remain the same:

  1. Declare where your libraries are located
  2. Require loading them in the correct order
  3. Ensure to load necessary plugins for your libraries (in this case, handlers for KnockoutJS)
  4. Initiate your application (named 'app' here). This is where you should set up your view models and bind them to DOM elements. At this stage, all libraries and plugins should be loaded.

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