Building Windows Apps with JavaScript Is Even Easier

Building Windows applications using JavaScript on Windows 10 is opening up new opportunities for developers. We cover how you can leverage your current web workflow for publishing code on the server while still having a single application published in the Windows store. This session covers the investments we’ve made for hosted content on the web including updates to the WebView control.
    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).

10 Common Mistakes Web Developers Make

web developer making a mistakeThere seems to be endless choices regarding how to accomplish the same task - to develop a website that works in today's modern web. Web developers have to choose a web hosting platform and underlying data storage, which tools to write HTML, CSS, and JavaScript in, how design will be implemented, and what potential JavaScript libraries/frameworks to include. Once choices are narrowed down, the online world is filled with articles, forums, and samples that provide tips for making a better web experience. Yet no matter which path is taken, all developers are susceptible to mistakes. Although some mistakes will be related to a specific approach, there are challenges shared among all web developers. So through research, experience, and recent observations, I thought I would share a list I compiled of ten common mistakes I see web developers make - and how to avoid them.

The following list is in no particular order.

1)  Writing old school HTML

Mistake: The early days of the internet had much less options for markup than we do today. However, old habits die hard, and many still write their HTML as if we were still in the 20th century. Examples here are using <table> elements for layout , <span> or <div> elements when other semantic-specific tags would be more appropriate, or using tags that are not supported in current HTML standard such as <center> or <font>, or spacing items on a page with a large number of &nbsp; entities.

Impact: Writing last decade's HTML can result in over complicated markup that will behave inconsistently across multiple browsers.

How to avoid: Stop using <table> element for layout of content, and limit usage for it to displaying tabular data. Get acquainted with the current markup options available such as seen at Use HTML to describe what the content is, not how it will be displayed. To display your content correctly, use CSS (

2 )  "It works in my browser…"

Mistake: A developer may be fond of a particular browser or really despise one, and might primarily test web pages with that bias in view. It is also possible that code samples found online may be written without factoring how it would render in other browsers. Also, some browsers have different default values for styles.

Impact: Writing a browser-centric site will likely result in very poor quality when displayed in other browsers.

How to avoid: It would not be practical to test web pages in every browser & version during development. However, having a regular interval of checking how your site will appear in multiple browsers is a good approach. Sites such as show snapshots of how a given page would render over multiple browsers/versions/platforms. Tools such as Visual Studio ( can also invoke multiple browsers to display a single page you are working on. When designing with CSS, consider "resetting" all the defaults as shown at

If your site is using any CSS features created specific for a browser, be cautious as to how you will approach vendor prefixes such as -webkit-, -moz-, or -ms-.  For guidance on industry trends in this regard, it would be worth your time to examine the following references:

While the above references explain a movement away from vendor prefixes and why, this site provides practical suggestions on how to work through this today.

3)  Bad form

Mistake: Prompting a user to provide any information (especially when entered into a text field) and assuming the data will be received as intended.

Impact: Many things can (and likely will) go wrong when user entry is trusted. Pages may fail if required data is not provided, or data received is not compatible with an underlying data scheme. Even more serious is the intentional violation of the site's database, perhaps through Injection attacks (see

How to avoid: The first bit of advice here is to make sure it is clear to the user what type of data you are looking for. These days, asking for an address could result in either a business, home, or even email address! In addition to be specific, take advantage of data validation techniques available in today's HTML as seen at this article No matter how data is validated on the browser side, be sure it is always validated on the server-side as well. Never allow a concatenated T-SQL statement to use data from user entry without confirmation the each field is the type of data it should be.

4)  Bloated responses

Mistake: The page is filled with many high quality graphics and/or pictures, scaled down with use of <img> element height and width attributes. Files linked from the page such as CSS and JavaScript are large. The source HTML markup may also be unnecessarily complex and extensive.

Impact: The time to have a page completely render becomes long enough for some users to give up or even impatiently re-request the whole page again. In some cases, errors will occur if page processing is waiting too long.

How to avoid: Don't adopt the mindset that access to the internet is getting faster and faster - thus allowing for bloated scenarios. Instead, consider everything going back and forth from the browser to your site as a cost. A major offender in page bloat is images.  To minimize the cost of images that slow down page loads, try these three tips:

  1. Ask yourself: "Are all my graphics absolutely necessary?" If not, remove unneeded images.
  2. Minimize the file size of your images with tools such as Shrink O'Matic or RIOT
  3. Preload images. This will not improve the cost on initial download, but can make other pages on site that use the images load much faster. For tips on this, see

Another way to reduce cost is to minify linked CSS and JavaScript files. There are plenty of tools out there to assist in this endeavor such as Minify CSS and Minify JS

Before we leave this topic, strive to be current with HTML (see mistake #1) and use good judgment when using <style> or <script> tags in HTML.

5)  Creating code that *should* work

Mistake: Whether it is JavaScript or code running on the server, a developer has tested and confirmed that it works, thereby concluding it should still work once deployed. The code executes without error trapping, because it worked when it was tested by developer.

Impact: Sites without proper error checking may reveal the errors to the end users in an ugly way. Not only can the user experience be dramatically impacted, the type of error message content could provide clues to a hacker as to how to infiltrate a site.

How to avoid: To err is human, so bring that philosophy to coding. With JavaScript, be sure to implement good techniques to prevent errors as well as catch them. Although this article addresses JavaScript coding for Windows Apps, the majority of the topics apply to web development too, and it is full of good tips! Another aid to help create solid code that can hold up well to future changes in code is unit testing (see

Failures in server-side code should be caught without the user seeing any of the nerdy details. Reveal only what is necessary, and be sure to set up friendly error pages for things like HTTP 404s (see

6)  Writing forking code

Mistake: With the noble notion of supporting all browsers and versions, a developer creates code to respond to each possible scenario. The code becomes a heap of if statements, forking in all sorts of direction.

Impact: As new versions of browsers update, management of code files become bulky and difficult to manage.

How to avoid: Implement feature detection in code versus browser/version detection. Feature detection techniques not only dramatically reduce the amount of code, it is much easier to read and manage. Consider using a library such as Modernizr ( which not only helps with feature detection, it also automatically helps provide fallback support for older browsers not up to speed with HTML5 or CSS3.

7)  Designing unresponsively

Mistake: Site development assumes viewing in the same size monitor as the developer/designer.

Impact: When viewing the site in mobile devices or very large screens, the user experience suffers with either not being able to see important aspects of the page or even preventing navigation to other pages.

How to avoid: Think responsively. Use responsive design (see in your sites. A very popular library ready to serve in this area is Bootstrap (

8)  Making meaningless pages

Mistake: Producing public facing pages with content that might be very useful, but not providing any hints to search engines. Accessibility features are not implemented.

Impact: Pages are not as discoverable through search engines and therefore may receive little or no visits. The page content may be very cryptic to users with impaired vision.

How to avoid: Use SEO (search engine optimizations) and support accessibility in HTML. Regarding SEO, be sure to add <meta> tags to provide meaning to a page with keywords and description. A good write up on that is found at To enable a better accessibility experience, be determined to provide an alt="your image description" attribute in each of your <img> or <area> tags. Of course, there is more to do and further suggestions can be investigated at You can also test a public web page at to see if it is compliant with Section 508 (

9)  Producing sites that are too refreshing

Mistake: Creating a site that requires full refreshes of a page for each interaction.

Impact: Similar to bloated pages (see mistake #4), performance of page loading time is affected. The user experience lacks fluidity, and each interaction could cause a brief (or long) resetting of the page.

How to avoid: One quick way to avoid this is by determining if posting back to the server is truly required. For example, client-side script can be used to provide immediate results when there is no dependency for server-side resources. You can also embrace AJAX techniques (see or go further with a single-page application “SPA” (see approach. Popular JavaScript libraries/frameworks are available to make adoption of these methods much easier, such as,, and

10)  Working too much

Mistake: A developer spends a long time creating web content. Time might be spent doing repetitive tasks, or simply typing a lot.

Impact: Time for initial web site launch or subsequent updates is too lengthy. Value of the developer diminishes when it appears other developers are doing comparable work in less time and with less effort. Manual labor is prone to mistakes, and troubleshooting mistakes takes even more time.

How to avoid: Explore your options. Consider using new tools or new process techniques for every stage of development. For example, how does your current code editor compare to Sublime Text ( or Visual Studio ( Regardless of what code editor you are using, have you recently dived into its features? Perhaps a small investment of your time perusing the documentation could unveil a new way to do something that could save hours & hours of time later. For example, note how an extension to Visual Studio can increase productivity for web developers as seen in this post

Don't miss out on tools available on the web to help! For example, check out the tools at to simplify testing (across multiple platforms and devices) and troubleshooting.

You can also help reduce time and mistakes by automating processes. An example of this is using a tool like Grunt ( that can automate things such as the minifying of files (see mistake #4). Another example is Bower ( which can help manage libraries/frameworks (see mistake #9).

How about the web server itself? With the help of services such as Microsoft Azure Web Apps (, you can quickly create a site for virtually any development scenario that can easily scale with your business!


By identifying common mistakes, web developers can eliminate much frustration that others have already endured. Not only is it important to acknowledge, but when we understand the impact of a mistake and take measures to avoid it, we can create a development process catered to our preferences – and do so with confidence!

    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).

Reveal Hidden Content Using Hash in URL

Suppose you have a web page that provides details on a given product.  The page has preloaded a number of products in HTML, but they are hidden from viewing via jQuery hide method.  If a user clicks a product link on the page, then the jQuery show method explicitly reveals it.  Now the user visits the page from another with a hash in URL like and the desired result is to automatically reveal the details for that product?  That was a question posed recently at StackOverflow, and this is how I answered it:

The key line of code above is line 11 of jqueryHash snippet. If the URL ended with #shoes, the details for that product would be automatically revealed. Note the code snippet does not do any validation of the hash (for brevity).

There were a number of answers given at the StackOverflow post, each with merit.  You can test my answer at my codepen testing grounds.

    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).

Universal Windows Apps with Angular

Starting with Visual Studio 2013 (with update 2), developers can create an app with a single solution to target multiple devices such as PCs, tablets, or phones.  This type of solution can generate universal Windows apps.  These can be written with C#, C++, or JavaScript. For video training on the topic, please check out the free course at the Microsoft Virtual Academy.

If written with JavaScript, web developers who use Angular will be happy to know you can continue to do so while making apps.

For a jumpstart on the development process, I have created a starter solution with a bare-bones shell that properly sets up Angular for use in the project.  The starter solution is named AngularVS (Angular for Visual Studio) and is available publicly at github.

A key factor for Angular to work properly in these types of apps is the use of the the ng-csp directive as seen below.  Not only will this enable Angular to work smoothly, if declared before other popular libraries|frameworks such as jQuery, it helps enable them safely too!


    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).
    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).

IsPrime Function in JavaScript

The following code sample illustrates how to use JavaScript to determine if a number provided is a prime number or not. In this example, the number is hardcoded in the JavaScript. You can edit this and experiment with other values at the isPrime at CodePen

var theNumber = 22;
var primeResult = isPrime(theNumber);
document.write("<hr />" + primeResult);

function isPrime(n) {

  var s = [2,3,5,7];
  var ld = [1,3,7,9]; 
  var divs = [];

  if (n==1) {return false;}
  if (s.indexOf(n) > -1) {return true;}
  if (ld.indexOf(n%10) > -1) {
     divs = getDivisibles(n);
  } else {
    return false;
  return (divs.length == 0);
}// isPrime

function getDivisibles(n) {
  var i = 2;
  var divs = [];
  while (i*i<=n) {
      if (n%i==0) {
        var upper = n/i;
        if (upper>i) {divs.push(upper);}
  }// while
  divs.sort(function(x,y){return x-y;});
  return divs;
}// getDivisibles

See the Pen isPrime by J Michael Palermo IV (@palermo4) on CodePen.

    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).

Demo jQuery Selectors

The demo below shows how to find a count of elements using different jQuery selectors. To modify the expressions yourself, feel free to make edits at the jQuery selectors demo at CodePen

$(document).ready(function () {
  // start the results of methods below with this:
  writeLine("Selectors<hr />");

  // count of all elements

  // count of elements in body
  writeSelectorLength("body *");

  // count of all divs and p tags

  // count of all p tags direct children of divs
  writeSelectorLength("div > p"); 

  // count of all li tags

// helper method to write content at specific location in page
function writeLine(anyHtml) {    
    var output = $("#output");
    var currentOutputContent = output.html();
    output.html(currentOutputContent += anyHtml + "<br />");
// helper method to write results of getSelectorLength
function writeSelectorLength(anySelector) {
// helper methos wrapping results of query in a span
function getSelectorLength(anySelector) {
    return anySelector + 
        "<span class='smaller'> has </span>" + 
        $(anySelector).length + 
        " <span class='smaller'>matches</span>";

See the Pen MVA140826-jQuery by J Michael Palermo IV (@palermo4) on CodePen.

    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).
    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).

Start Developing for Windows (8.1) Store Apps using HTML5

jumpstartstudioWhen Windows 8 was first introduced, a huge opportunity opened up for web developers.  How so?  Anyone with HTML, CSS, and JavaScript skills could now apply such skills to developing apps, not just sites.  This is due to Microsoft supporting the development of WinRT apps with either C++, .NET, and/or JavaScript.  How different is it from writing a web site vs. an app?  If you are a web developer and you want to find out, be sure to look at the DevRadio episodes on developing for Windows 8 in half the time (4 minute videos) or the comprehensive “jump start” training series on HTML5 for Windows 8.  Moving onward, it will be assumed you already have a degree of experience with developing apps for Windows 8 using HTML5, and you are interested in what’s new or changed.

With Windows 8.1, consumers will enjoy a richer, more interactive experience. Correspondingly, the  APIs have been updated, providing developers either new or easier ways of doing things. A listing of the API deltas can be found at the Windows Dev Center for Windows Store apps.  Our focus right now is not to do a tedious overview of everything new.  Rather, we will look at what you need to do to get ramped up with some highlighted features as quick as possible.

Developer Requirements

To get started, you will need to install Windows 8.1 (preview is available for download) and Visual Studio 2013 (preview is available for download).  You should also highly consider registering at the App Builder site for relevant resources.

Visual Studio 2013 Updates

Creating a new project with Visual Studio 2013 is much like it was with Visual Studio 2012.  Consider the following screen capture of the “New Project” dialogue box:


First point of interest is a new template type named “Hub App” which allows for a hierarchical system of navigation. The template uses a new Hub control, and you can learn more about it if you download the Hub control sample. Regardless of which template type used though, let’s examine some core changes. 

WinJS 2.0

The source page of HTML files now target Windows 8.1, as indicated by the references to WinJS 2.0 as seen here:

<!-- WinJS references -->
<link href="//Microsoft.WinJS.2.0.Preview/css/ui-light.css" 
     rel="stylesheet" /> <script src="//Microsoft.WinJS.2.0.Preview/js/base.js"></script> <script src="//Microsoft.WinJS.2.0.Preview/js/ui.js"></script>

You will also see this visually in the solution explorer view.  When expanded, it is easy to see the resources being requested as seen here:


Note that when you open a project created for Windows 8, Visual Studio 2013 will prompt you to determine if the project should now target Windows 8.1

Editor Enhancements

A pleasant enhancement to the JavaScript editor is the automatic completion of code blocks when typing the left side of the block.  For example, when typing a left brace { , the editor will pair it with a right brace } and auto-format along the way.  Other pairings include parenthesis, brackets, and quotation marks (single or double).

The editor will also highlight identifiers when selected.  For example, if a variable is declared with the name isAwesome, notice how the editor will highlight where else it is used:



One more quick change to be aware of is found in the package.appxmanifest file.  When opening in Visual Studio 2013, you will find the Application UI tab where you can configure the images used for your apps tiles.  However, notice the new options as seen here:


These new options introduce both a larger and smaller tile.  You should support these new tile sizes so that users of Windows 8.1 can easily organize their Start screen.  The example below shows the 70x70 in upper left, 150x150 in upper middle, 310x150 in the lower left, and the 310x310 on the right:

What Next?

So much could be next.  To some degree that will depend on the type of app you are developing.  The information covered so far is to enable a quick start to the development process.  By setting up the required environment and understanding a few of the changes in Visual Studio 2013, you can start coding as usual.  Look for deeper looks at specific features in the near future!

    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).

HTML5 Apps 70-480

Elevate! Electrify!


Jeremy Foster and I had no idea what kind of response resulted from presenting our free training course to prepare for the 70-480 exam.  For example, who knew that our shirts (purchased from the Microsoft Store the day prior) would become so popular, people contacting both of us wondering where they could buy one?

That said, the real story is in the successful outcomes of those who watched the videos and then subsequently passed the exam.  Even more impressive to me personally is that some already have apps submitted to the Windows Store!  (Do you have an app in the store? If not, consider 30,000 reasons why you should submit your app now!)

A Jump Start to the Jump Start

I want to give a Matthew Hughes in the United Kingdom recognition for his outstanding coverage of this course.  He took meticulous, detailed notes on every topic.  I have organized his blog posts below:

Part 0    Getting Started

Part 1    Semantic Markup, Forms, Media and SVG

Part 2    Cascading Style Sheets (CSS)

Part 3    Advanced Layouts and Animations

Part 4    JavaScript Core Capabilities

Part 5    Manipulating the DOM

Part 6    Advanced Topics

    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).