jquery-mobile interview questions
Top jquery-mobile frequently asked interview questions
I wonder if I were to develop a mobile Web app (now, in two weeks, or in a month), which one should I go for? Which one would you mobile Web developers go for?
If jQM 1.0 were officially released today, I would most likely embrace it (as long as it actually delivers what it promises). Now that it is in alpha, I wonder whether it is worth to jump into it yet for a commercial grade project? Would Sencha Touch be a better alternative?
Source: (StackOverflow)
Does the jQuery Mobile framework have a way of centering elements, specifically buttons? It looks like it defaults to left-aligning everything and I can't find a way (within the framework) to do this.
Source: (StackOverflow)
My phonegap/jquery mobile application flickers most of the time when I navigate between the pages. Is this normal or is there a solution for this?
Source: (StackOverflow)
Is there any way, bearing in mind the way the jQuert Mobile framework operates, to fix the page so that the footer always aligns with the bottom of the page - no matter the height.
As it stands the height of a jQuery page will change, especially as devices are rotated portrait to landscape, so the solution would have to take this into account.
Just to clarify - I dont need the footer to be at the bottom of viewport, just working so that the default page height doesn't drop below the viewport height
Thanks
Source: (StackOverflow)
I am using JQuery Mobile and I am having trouble understanding differences between classic document ready and jQuery Mobile page events.
Can someone tell me what is the real difference?
Why should
$(document).ready() {
});
be better than
$(document).on('pageinit') {
});
What is the order of page events, when you transition from one page to another?
How can I send data from one page to another and is it possible to access data from previous page?
Source: (StackOverflow)
I'm new to mobile web development, and I just made a mobile-app with PhoneGap, employing frequent use of jQuery.
But there were naturally a couple of glitches related to how I formatted things and the way they actually appeared on the mobile device screens I was testing with, and in trying to work these out I stumbled across many suggestions to make things easier on myself by using jQuery mobile.
Now this confuses me-- jQuery had no roll in formatting. That was just my beginner's level knowledge of mobile CSS that caused the problems.
So what exactly does jQuery mobile do, and how is it different from ordinary jQuery? If I already know jQuery, what's going to be new to me?
Source: (StackOverflow)
I am linking to the jQuery Mobile stylesheet on a CDN and would like to fall back to my local version of the stylesheet if the CDN fails. For scripts the solution is well known:
<!-- Load jQuery and jQuery mobile with fall back to local server -->
<script src="http://code.jquery.com/jquery-1.6.3.min.js"></script>
<script type="text/javascript">
if (typeof jQuery == 'undefined') {
document.write(unescape("%3Cscript src='jquery-1.6.3.min.js'%3E"));
}
</script>
I would like to do something similar for a style sheet:
<link rel="stylesheet" rel='nofollow' href="http://code.jquery.com/mobile/1.0b3/jquery.mobile-1.0b3.min.css" />
I am not sure if a similar approach can be achieved because I am not sure whether the browser blocks in the same way when linking a script as it does when loading a script (maybe it is possible to load a stylesheet in a script tag and then inject it into the page) ?
So my question is: How do I ensure a stylesheet is loaded locally if a CDN fails ?
Source: (StackOverflow)
I am using JQuery Mobile version 4.1a and using:
data-position="fixed"
on both header and footer.
When I scroll the content it disappears and then appears again.
Is there any way to make it stay in it's position and not disappear everytime I scroll the page?
Thanks
Source: (StackOverflow)
I am buildin a mobile web app with jquery mobile and
I want to check if a checkbox is checked. Here is my code.
<script type=text/javascript>
function validate(){
if (remember.checked == 1){
alert("checked") ;
}else{
alert("You didn't check it! Let me check it for you.")
}
}
</script>
<input id="remember" name="remember" type="checkbox" onclick="validate()" />
But for some reason or another it doesn't execute it.
Please help !
----EDIT-----
This is what I have for the moment.
<DIV data-role="content" data-theme="g">
<DIV class=ui-grid-g-login>
<FORM method=post action=[$=PROBE(266)/] data-theme="C">
<P>~DATA_ERROR~</P>
<div id="mail" data-role="fieldcontain">
<label for="mail">Email:*</label>
<input id="mail" name="mail" type="email" />
</div>
<div id="pass" data-role="fieldcontain">
<label for="pass">Paswoord:*</label>
<input id="pass" name="pass" type="password" />
</div>
<div id="remember" data-role="fieldcontain">
<label for="remember">Onthoud mij</label>
<input id="remember" name="remember" type="checkbox" onclick="validate()" />
</div>
<P><INPUT class=btn name=submit value=Login type=submit onclick="validate()"></P>
</FORM>
</DIV>
</DIV><!-- /content -->
<script type=text/javascript>
function validate(){
var remember = document.getElementById('remember');
if (remember.checked){
alert("checked") ;
}else{
alert("You didn't check it! Let me check it for you.")
}
}
</script>
----EDIT--
Solved it, the problem was that the fieldcontain was also named 'remember'
Source: (StackOverflow)
What is the correct way (to this date) to use JQuery Mobile and Phonegap together?
Both frameworks need to load before they can be used. How can I be sure that both are loaded before I can use them?
Source: (StackOverflow)
I would like to build a mobile app, brewed from nothing more but html/css and JavaScript. While I have a decent knowledge of how to build a web app with JavaScript, I thought I might have a look into a framework like jquery-mobile.
At first, I thought jquery-mobile was nothing more then a widget framework which targets mobile browsers. Very similar to jquery-ui but for the mobile world. But I noticed that jquery-mobile is more than that. It comes with a bunch of architecture and let's you create apps with a declarative html syntax. So for the most easy thinkable app, you wouldn't need to write a single line of JavaScript by yourself (which is cool, because we all like to work less, don't we?)
To support the approach of creating apps using a declarative html syntax, I think it's a good take to combine jquery-mobile with knockoutjs. Knockoutjs is a client-side MVVM framework that aims to bring MVVM super powers known from WPF/Silverlight to the JavaScript world.
For me MVVM is a new world. While I have already read a lot about it, I have never actually used it myself before.
So this posting is about how to architecture an app using jquery-mobile and knockoutjs together. My idea was to write down the approach that I came up with after looking at it for several hours, and have some jquery-mobile/knockout yoda to comment it, showing me why it sucks and why I shouldn't do programming in the first place ;-)
The html
jquery-mobile does a good job providing a basic structure model of pages. While I am well aware that I could have my pages to be loaded via ajax afterwards, I just decided to keep all of them in one index.html file. In this basic scenario we are talking about two pages so that it shouldn't be too hard to stay on top of things.
<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
<link rel="stylesheet" rel='nofollow' href="libs/jquery-mobile/jquery.mobile-1.0a4.1.css" />
<link rel="stylesheet" rel='nofollow' href="app/base/css/base.css" />
<script src="libs/jquery/jquery-1.5.0.min.js"></script>
<script src="libs/knockout/knockout-1.2.0.js"></script>
<script src="libs/knockout/knockout-bindings-jqm.js" type="text/javascript"></script>
<script src="libs/rx/rx.js" type="text/javascript"></script>
<script src="app/App.js"></script>
<script src="app/App.ViewModels.HomeScreenViewModel.js"></script>
<script src="app/App.MockedStatisticsService.js"></script>
<script src="libs/jquery-mobile/jquery.mobile-1.0a4.1.js"></script>
</head>
<body>
<!-- Start of first page -->
<div data-role="page" id="home">
<div data-role="header">
<h1>Demo App</h1>
</div><!-- /header -->
<div data-role="content">
<div class="ui-grid-a">
<div class="ui-block-a">
<div class="ui-bar" style="height:120px">
<h1>Tours today (please wait 10 seconds to see the effect)</h1>
<p><span data-bind="text: toursTotal"></span> total</p>
<p><span data-bind="text: toursRunning"></span> running</p>
<p><span data-bind="text: toursCompleted"></span> completed</p>
</div>
</div>
</div>
<fieldset class="ui-grid-a">
<div class="ui-block-a"><button data-bind="click: showTourList, jqmButtonEnabled: toursAvailable" data-theme="a">Tour List</button></div>
</fieldset>
</div><!-- /content -->
<div data-role="footer" data-position="fixed">
<h4>by Christoph Burgdorf</h4>
</div><!-- /header -->
</div><!-- /page -->
<!-- tourlist page -->
<div data-role="page" id="tourlist">
<div data-role="header">
<h1>Bar</h1>
</div><!-- /header -->
<div data-role="content">
<p><a rel='nofollow' href="#home">Back to home</a></p>
</div><!-- /content -->
<div data-role="footer" data-position="fixed">
<h4>by Christoph Burgdorf</h4>
</div><!-- /header -->
</div><!-- /page -->
</body>
</html>
The JavaScript
So let's come to the fun part - the JavaScript!
When I started to think about layering the app, I have had several things in mind (e.g. testability, loose coupling). I'm going to show you how I decided to split of my files and comment things like why did I choose one thing over another while I go...
App.js
var App = window.App = {};
App.ViewModels = {};
$(document).bind('mobileinit', function(){
// while app is running use App.Service.mockStatistic({ToursCompleted: 45}); to fake backend data from the console
var service = App.Service = new App.MockedStatisticService();
$('#home').live('pagecreate', function(event, ui){
var viewModel = new App.ViewModels.HomeScreenViewModel(service);
ko.applyBindings(viewModel, this);
viewModel.startServicePolling();
});
});
App.js is the entry point of my app. It creates the App object and provides a namespace for the view models (soon to come). It listenes for the mobileinit event which jquery-mobile provides.
As you can see, I'm creating a instance of some kind of ajax service (which we will look at later) and save it to the variable "service".
I also hook up the pagecreate event for the home page in which I create an instance of the viewModel that gets the service instance passed in. This point is essential to me. If anybody thinks, this should be done differently, please share your thoughts!
The point is, the view model needs to operate on a service (GetTour/, SaveTour etc.). But I don't want the ViewModel to know any more about it. So for example, in our case, I'm just passing in a mocked ajax service because the backend hasn't been developed yet.
Another thing I should mention is that the ViewModel has zero knowledge about the actual view. That's why I'm calling ko.applyBindings(viewModel, this) from within the pagecreate handler. I wanted to keep the view model seperated from the actual view to make it easier to test it.
App.ViewModels.HomeScreenViewModel.js
(function(App){
App.ViewModels.HomeScreenViewModel = function(service){
var self = {}, disposableServicePoller = Rx.Disposable.Empty;
self.toursTotal = ko.observable(0);
self.toursRunning = ko.observable(0);
self.toursCompleted = ko.observable(0);
self.toursAvailable = ko.dependentObservable(function(){ return this.toursTotal() > 0; }, self);
self.showTourList = function(){ $.mobile.changePage('#tourlist', 'pop', false, true); };
self.startServicePolling = function(){
disposableServicePoller = Rx.Observable
.Interval(10000)
.Select(service.getStatistics)
.Switch()
.Subscribe(function(statistics){
self.toursTotal(statistics.ToursTotal);
self.toursRunning(statistics.ToursRunning);
self.toursCompleted(statistics.ToursCompleted);
});
};
self.stopServicePolling = disposableServicePoller.Dispose;
return self;
};
})(App)
While you will find most knockoutjs view model examples using an object literal syntax, I'm using the traditional function syntax with a 'self' helper objects. Basically, it's a matter of taste. But when you want to have one observable property to reference another, you can't write down the object literal in one go which makes it less symmetric. That's one of the reason why I'm choosing a different syntax.
The next reason is the service that I can pass on as a parameter as I mentioned before.
There is one more thing with this view model which I'm not sure if I did choose the right way. I want to poll the ajax service periodically to fetch the results from the server. So, I have choosen to implement startServicePolling/*stopServicePolling* methods to do so. The idea is to start the polling on pageshow, and stop it when the user navigates to different page.
You can ignore the syntax which is used to poll the service. It's RxJS magic. Just be sure I'm polling it and update the observable properties with the returned result as you can see in the Subscribe(function(statistics){..}) part.
App.MockedStatisticsService.js
Ok, there is just one thing left to show you. It's the actual service implementation. I'm not going much into detail here. It's just a mock that returns some numbers when getStatistics is called. There is another method mockStatistics which I use to set new values through the browsers js console while the app is running.
(function(App){
App.MockedStatisticService = function(){
var self = {},
defaultStatistic = {
ToursTotal: 505,
ToursRunning: 110,
ToursCompleted: 115
},
currentStatistic = $.extend({}, defaultStatistic);;
self.mockStatistic = function(statistics){
currentStatistic = $.extend({}, defaultStatistic, statistics);
};
self.getStatistics = function(){
var asyncSubject = new Rx.AsyncSubject();
asyncSubject.OnNext(currentStatistic);
asyncSubject.OnCompleted();
return asyncSubject.AsObservable();
};
return self;
};
})(App)
Ok, I wrote much more as I initially planned to write. My finger hurt, my dogs are asking me to take them for a walk and I feel exhausted. I'm sure there are plenty things missing here and that I put in a bunch of typos and grammer mistakes. Yell at me if something isn't clear and I will update the posting later.
The posting might not seem as an question but actually it is! I would like you to share your thoughts about my approach and if you think it's good or bad or if I'm missing out things.
UPDATE
Due to the major popularity this posting gained and because several people asked me to do so, I have put the code of this example on github:
https://github.com/cburgdorf/stackoverflow-knockout-example
Get it while it's hot!
Source: (StackOverflow)
I'm new to web development and there are just too many j* stuff out there. I wonder what are the differences between these frameworks?
Moreover, why do people talk a lot about making a plugin using jQuery? Isn't it supposed to be a JavaScript library to make your web page more interactive?
Source: (StackOverflow)
Does anyone know of a really good tutorial or sample project where Phonegap and jQuery Mobile is used for a real world example?
All the examples I found were showing fancy transitions or theming in jQuery Mobile. The Phonegap examples mostly showcases the Phonegap API.
I could not find a single example where Phonegap and jQuery Mobile was used to solve real world problems, such as writing a app that combines Phonegap and jQuery Mobile to do user input validation, saving the data, uploading data to a web service, etc.
Source: (StackOverflow)
I'm going to make a native (meaning; not in the browser) mobile app. Since I'm a web-developer I'm struggling to decide whether or not I should try Phonegap or just build an native app in java or objective-c.
The app requirements are simple. GPS/wifi location, Facebook integration and I guess I'll need a database to handle some of the application specific Facebook-friend relations. Like the highscores in a game, for example - stuff like that.
I'm a web-developer, and don't know neither java or objective-c, yet. I've never used Phonegap before, so I don't know if it's capable of fulfilling my requirements.
So my question is as follows;
Can I use Phonegap for my app, or do I need to dive into a new language?
Source: (StackOverflow)
I am struggling somewhat with pre-compilation of templates in Handlebars. My jQuery Mobile project is getting pretty big template-wise and I wish to pre-compile the templates I use.
However I can't seem to find a good explanation (like a step by step tutorial) of how to do this with Handlebars.
I still have my templates all inline using the script tags. I have handlebars installed using NPM. But now I am kinda lost in how to proceed.
I am guessing doing something like
handlebars -s event.handlebars > event.compiled
and somehow including the event.compiled contents? But then, how to call it.
I am calling my templates like so
var source = $('#tmpl_profile').html(),
template = Handlebars.compile(source),
context = user.profile()),
html = template(context);
Hope someone can shed some light on this for me.
Source: (StackOverflow)