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JavaScript
Tuesday, September 25, 2012PrintSubscribe
jQuery Cross-Domain Dynamic Client of a Web App

A fictitious company Northwind Traders had a fair amount of success with the statically exposed product catalog that allows third parties to display the catalog on their own web sites. An exceptionally small amount of code is required to create a jQuery cross-domain static client of the back office web app created with Code On Time.

Northwind Traders have decided to offer search capabilities of the back office web app to their premium integration partners.

A possible implementation of a search client is shown next.

If a user clicks Find without entering a search sample,  then the first one hundred products are retrieved in alphabetical order.

The search result displayed in jQuery cross-domain dynamic client of the demo web app when a search criteria is not specified

This is the result that matches “40 biscuit” search criteria.

The search result displayed in jQuery cross-domain dynamic client of the demo web app with '40 biscuit' search sample

The back office web app at http://demo.codeontime.com/northwind/pages/products.aspx displays the same exact result as follows.

The 'Quick Find' result for '40 biscuit' search sample in the demo web app created with Code On Time

The HTML page implementing a sample search client works across domains in any web browser.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>jQuery Cross-Domain Client</title>
    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.1/jquery.min.js"></script>
    <script type="text/javascript">
        $(document).ready(function () {
            $('#ProductListPanel').hide();
            $('#Query').focus();
            $('#FindButton').click(function (e) {
                e.preventDefault();
                var query = '?_sortExpression=ProductName&_q=' +
                    encodeURIComponent($('#Query').val());
                $.ajax({
                    url: 'http://demo.codeontime.com/northwind/appservices/Products' + query,
                    cache: false,
                    dataType: 'jsonp',
                    success: function (data) {
                        $('#ProductList option').remove();
                        $.each(data.Products, function (index, product) {
                            $('<option>')
                                .text(
                                    product.ProductName + ' / ' +
                                    product.CategoryCategoryName + ' / ' +
                                    product.SupplierCompanyName + ' / ' +
                                    product.UnitPrice)
                                .attr('value', product.ProductID)
                                .appendTo($('#ProductList'));
                        });
                        $('#ProductListPanel').show();
                    }
                });
            });
        });
    </script>
</head>
<body>
    <input id="Query" type="text" />
    <button id="FindButton">
        Find</button>
    <div id="ProductListPanel">
        <select id="ProductList" size="10">
        </select>
    </div>
</body>
</html>

The page statically links jQuery library from CDN provided by Google.

The search starts when a user clicks on the Find button.

The “click” handler declares a query variable that contains “_sortExpression” and “_q” parameters. The first parameter specifies the sort order of returned products. The search parameter “_q” is the sample for the Quick Find feature of the web app.

Next, the “click” handler invokes ajax method to retrieve data from the web app. The key parameters of the method are url and dataType. The first parameter defines the REST URI of Products data controller. The second parameter indicates that a cross-domain web request must be executed by jQuery library.

If the request is successful, then a list of products populates the list box.

Monday, September 24, 2012PrintSubscribe
jQuery Cross-Domain Static Client of a Web App

Integration with other service providers is a key to success of many SaaS business applications. The mail order company Northwind Traders has decided to expose their product catalog to third parties to increase sales. A back office web app has been created with Code On Time and configured to expose the product catalog.

An integration partner can put together a simple HTML page to display a list of products from http://demo.codeontime.com/northwind with a very few lines of code.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>jQuery Cross-Domain Client</title>
    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.1/jquery.min.js"></script>
    <script src="http://demo.codeontime.com/northwind/appservices/Products?_instance=ProductCatalog">
    </script>
    <script type="text/javascript">
        $(document).ready(function () {
            $.each(MyCompany.ProductCatalog.Products, function (index, product) {
                $('<option>')
                    .text(
                        product.ProductName + ' / ' +
                        product.CategoryCategoryName + ' / ' +
                        product.SupplierCompanyName + ' / ' +
                        product.UnitPrice)
                    .attr('value', product.ProductID)
                    .appendTo($('#ProductList'));
            });
        });
    </script>
</head>
<body>
    <select id="ProductList" size="20">
    </select>
</body>
</html>

The first script tag links jQuery library to the page straight from the Google’s CDN.

The second script references http://demo.codeontime.com/northwind/appservices/Products. This URL points to the demo web app. The highlighted component /appservices/Products references the REST URI of the Products data controller. The _instance parameter instructs the application to construct a JavaScript property with the name of ProductCatalog. The property will be assigned to MyCompany global variable that matches the namespace of the application.

The script executes as soon as the page has been loaded in the browser and iterates through MyCompany.ProductCatalog.Products array to populate the select element ProductList defined in the page body.

This is how the page will look if you have it opened in your default web browser.

A jQuery cross-domain static client of a web app in action

If you open the page straight from the hard drive in Internet Explorer, then you many need to allow running scripts for the list of products to get displayed.

Internet Explorer will prompt to Allow Blocked Content if the jQuery cross-domain static client file is opened directly from the file system

The product catalog is dynamically constructed by the web app every time it is requested.

This is how the array of products look in debug mode if global variable MyCompany is inspected in Visual Studio.

Global variable 'MyCompany' of a jQuery cross-domain static client of the demo web app is inspected in Visual Studio at runtime

If more than one resource pointing to the demo app controller is linked to the page then data will be available as properties of MyCompany global variable.

The Product Catalog data is downloaded by a web browser from the demo web app regardless of the domain of the HTML page or web platform that has served the page. This opens tremendous opportunities of integrating data in the third-party solutions.

Tuesday, August 7, 2012PrintSubscribe
Debugging Custom Input Elements

Implementation of input element enhancements may be very simple or demand a relatively complex code. The client input elements are written in JavaScript and may require debugging.

The first instinct of any developer is to write some code, run the app, and try the code in action. Developing and debugging a custom input element with the entire web application project may become unproductive – you need to sign in, navigate to the correct page, select a view to force the custom input element to be activated. Each step takes valuable time.

We recommend creating a test HTML page and debugging the app without touching the actual application.

Let’s consider creating a test HTML page for the Reorder Level Slider input element shown in this screen shot of a live application.

The custom slider input element attached to 'ReorderLevel' data field in a Code On Time web application

If you have followed the instruction from the tutorial then you have the following folder structure under [Documents]\Code On Time\Client folder.

A standalone html page can be used to debug custom input elements without the need to have them run in the actual application

Create the HTML file ReorderLevelDebugger.htm with the following content in Visual Studio or your favorite text editor.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Edtior Debugger</title>
    <link type="text/css" rel="Stylesheet" href="../../../Library/_Client/Stylesheets/_System/_System.css" />
    <script type="text/javascript" src="../../../Library/Data Aquarium/Scripts/_System.js"></script>
    <!-- 
         Important: 
         link the file(s) that you are debugging after the reference to _System.js 
     -->
    <script type="text/javascript" src="ReorderLevelSlider.js"></script>
    <script type="text/javascript">
        // this code is the emulation of steps executed by the client library
        var reorderLevelEditorFactory = null;
        $(function () {
            // create a slider factory object
            reorderLevelEditorFactory = new MyCompany$ReorderLevelSlider()
            // initialize the debugging buttons
            $('#Attach').click(function () {
                reorderLevelEditorFactory.attach($('#Input1').get(), 'Form');
            });
            $('#Detach').click(function () {
                reorderLevelEditorFactory.detach($('#Input1').get(), 'Form');
            });
        });
    </script>
</head>
<body>
    <div>
        Testing the "Reorder Level" slider:
    </div>
    <div>
        <button id="Attach">
            Attach</button>
        <button id="Detach">
            Detach</button></div>
    <div style="border: solid 1px silver; padding: 8px; margin-top: 8px;">
        <input type="text" id="Input1" value="35" />
    </div>
</body>
</html>

The file declares a script block with the global instance of MyCompany$ReorderLevelSlider object. The startup script also assigns click handlers for Attach and Detach buttons declared in the page body. The script header links the system script and stylesheet included by the code generator in every application.

Save the file and open it in the web browser. This is how the page is rendered in Internet Explorer 9 if you click on the file name in Windows Explorer.

Html debugger displayed in Internet Explorer requires user to enable JavaScript execution

You will need to allow execution of JavaScript in the local webpage. This will not be necessary if you preview the page by selecting View in Browser (Ctrl+Shift+W) in the Visual Studio development environment.

The custom input element HTML debugger page with JavaScript enabled

Click Attach button to see the slider attached to the input field.

The slider is attached to the input element when a user clicks on 'Attach' button

Move the slider to try it out.

The custom input element in action

Click Detach  button to see the slider removed.

The custom input element is removed when a user clicks on 'Detach' button

Buttons Attach and Detach invoke the corresponding methods of the “factory” object to associate custom input enhancement with the input field and to have them removed. This is exactly the same pattern of execution by the client library in the live web application.