JavaScript

AngularJS Directive… preloader experiment

I’m still a newbie to AngularJS development, however I have to admit that I’m having a lot of fun thinking of new directives and exploring increasingly better ways to implement them, mostly inspired by the lively and vital AngularJS community.

I’m posting one of my most recent experiments which was to have a very simple way to add preloading functionality to an AngularJS application… and this i what I came up with.

Please note that this is purely experimental and the reason for me posting it is to allow others to start thinking of their own directives as well as learn something in the process..

Now… one of my objectives was that I wanted to be able to point to an external file for the preloader content, however the preloader content should also be able to contain AngularJS itself.

This lead me to the use of the AngularJS-native “include” directive and the “$compile” service.

The actual implementation of the loading was out of scope for this small experiment, so I decided to fake it with a simple timer using the relatively new “$timeout” service, which recently replaced the “$defer” service as a way of postponing function calls.

Furthermore, since basically every application I build contains some level of DOM manipulation, I have no problem with having jQuery as a pre-requisite, so the implementation is using jQuery for the DOM manipulation, however it would be trivial to remove or replace this requirement.

AngularJS Community Member, Glen Maddern, has been so kind to post my experiment as a executing sample in the form of a Gist on GitHub:
http://2886724.run-a-gist.herokuapp.com/

The contents of the splash.html is very crude for this example, however it could be any HTML content…

<h1 ng-click="clickHandler(event)" ng-controller="PreloaderController">
	Loading, please wait...still loading {{percentCompleted}}%
</h1>

As you can see in the the snippet above, the preloader HTML is driven by a PreloaderController… and it has a clickHandler for demo purposes to shurtcut the preloading…

function PreloaderController( $scope, $timeout ) {

	$scope.percentCompleted = 0;

	$scope.applicationProgressMock = function() {

		if( $scope.percentCompleted == 100 ) {
			$scope.$emit( "applicationComplete" );
		}
		else
		{
			$scope.percentCompleted += 5;
			$timeout( $scope.applicationProgressMock, 100 );
		}
	}
	$timeout( $scope.applicationProgressMock, 100 );

	$scope.clickHandler = function( event ) {
		$scope.percentCompleted = 100;
	}
}

The directive itself is fairly simple and straightforward JavaScript…

PreloaderFactory = function( $compile ) {

	var directive = {

		restrict : "A",

		link : function( scope, elm, attrs ) {

			scope.preloader = jQuery( "<ng-include />" );
			scope.preloader.attr( "src", "'"+ attrs.preloader +".html'" );

			$compile( scope.preloader )( scope );

			jQuery( "body" ).append( scope.preloader );

			scope.$on( "applicationComplete", function( event ) {

				jQuery( scope.preloader ).remove();
			});
		}
	}
	return directive;
}

Now, my main HTML looks like this, pretty advanced app…

<html ng-app="application" preloader="splash">
  <head>
    
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
    
    <title>Preloader Experiment</title>
    
    <script src="http://code.angularjs.org/angular-1.0.0rc10.min.js"></script>
    <script src="http://code.jquery.com/jquery-1.7.2.min.js"></script>
    <script src="preloader-0.0.1.js"></script>
    
    <script>
    
    	angular.module( "application", [] )
    	
    	.directive( "preloader", PreloaderFactory );
    	
    </script>
    
  </head>
  <body>
  
  </body>
</html>

That’s it, a faily simple and crude implementation of a preloader tag… comments are much appreciated, however please note that this was purely intended as an inspiration and not a cookbook recipe…

In any case I decided to put it on GitHub… I sincerely hope to be able to get much more samples up there and that they will increase in quality…
https://github.com/pmoelgaard/labs/tree/master/angular/preloader-directive

CookBook

How to implement a BLINK tag in AngularJS

One of the features of early HTML that is so uncool that it’s so extremely cool now that it has taken epic proportions, is that much celebrated as well as hated BLINK tag…

Now, it disappeared from most implementations due to the massive criticism it received, In 1996 Jakob Nielsen even described the element as “simply evil” in his Alertbox column Top Ten Mistakes in Web Design.

Anyways, its back for the ones who think it could be a fun little thing to add anywhere, and now with AngularJS… let me just add, that I think it would be a horrible idea to put it in any website short of being a tribute website to horrible websites from the 80’s…


var blink = angular.module('blink', [])
    .directive('blink', function($timeout) {
    return {
        restrict: 'E',
        transclude: true,
        scope: {},
        controller: function($scope, $element) {
            function showElement() {
                $element.css("display", "inline");
                $timeout(hideElement, 1000);
            }

            function hideElement() {
                $element.css("display", "none");
                $timeout(showElement, 1000);
            }
            showElement();
        },
        template: '<span ng-transclude></span>',
        replace: true
    };
});​

Using it from HTML would be as simple as this…


<div ng-app="blink">
    <blink>Forward Thinking</blink>
</div>​

You can check out the JSFiddle here…
http://jsfiddle.net/qy7Bt/59/

The initial implementation was created by Søren Kyndi-Wiuff and it was then later refined to support a more mature version of AngularJS by Misko Hevery, both guys heavy-weight contributors to AngularJS… helped along the way by Mr. Ganaraj who was kind enough to point out and illustrate deprecated parts of the AngularJS…

Check out AngularJS if you haven’t done so yet and you are in the process of working on HTML systems, this is how HTML would have been if it had been created for Applications…
angularjs.org

Tools, Uncategorized

Trello… now with an API (Beta)

Trello is not only a very useful task management system, incorporating SCRUM board approach with HTML5 and an exceptional nice look and feel… now it also has a very elegant REST API.

Check it out…
https://trello.com/docs/

Here is a quick sample on how to retrieve the cards for the current user… using the Client.js JavaScript class that Trello is providing asn easy way to get started…
http://jsfiddle.net/nNesx/

They have opened up their development plans in the form of their internal development board…
https://trello.com/api

JavaScript

AppJS… Build Cross-Platform Applications

…for desktop using HTML, CSS, Javascript !

It’s still very early stuff, however its interesting to see how a lightweight container like this may develop into something pretty useful, at least the stack of technologies used is entirely aligned with how I would set out to build a lightweight app container…

Why AppJS?

Because it is simple and yet powerful. Using AppJS you don’t need to be worry about coding cross-platform or learning new languages and tools. You are already familiar with HTML, CSS and Javascript. What is better than this stack for application development? Beside, AppJS uses Chromium at the core so you get latest HTML 5 APIs working. So relax and focus on the task your application should do.

HTML 5

AppJS allows you to use HTML 5 APIs to create attractive applications from Word Processors to 3D Games. You are no longer limited to default GUI widgets that plaforms force you to use. Creating custom UIs is now only limited to your imagination!

CSS 3

Using CSS you can decorate widgets as you like. Create a custom widget in HTML and complete your work with decorating it. Adding shadows, animating elements and transforming objects in 3D space are a few examples of what you can do with CSS 3.

Node.js

The interesting part of AppJS is that it uses Node.js as the backbone. Node.js has been built to ease the process of developing scalable network applications. But today, you can see Node nearly everywhere! It has a nice API and lots of modules.

Check it out…
http://appjs.org/

JavaScript

FixieJS… a tremendously cool html utility

Fixie.js is an open source tool that automatically adds filler content to HTML documents.

Image

Adding lorem ipsum text to HTML documents involves copy-pasting, manual editing, and increasingly unwieldy code.

By interpreting your semantic HTML5 tags, Fixie will automagically add the right type of content in the right places. Headings, paragraphs, links, images, sections… trust me, it’s all there. That way you can focus on your design, instead of finding the right filler content.

A nice example on how this can be useful can be found in the equally clever utility: FlickHoldr
http://flickholdr.com/

Image

FlickHoldr simply gets placeholders related to the site you are developing, by pulling images from flickr based on tags… very simple and elegant…

JavaScript

AngularJS… a selection-change directive… an early implementation

having run into some issue implementing a change handler on the select control without setting the model property… I decided to see how it could be to implement a selectionHandler directive…

I started out with this implementation which obviously is far from best practice and far from ideal yet… next step will be to find the best practice to implement a tag for an entire “combobox”…

HTML

<select ng-datasource="candidateContacts" ng-selection-change="selectContact">
	<option ng-repeat="candidateContact in candidateContacts" ng-selected="candidateContact.id == contact.item.id">
		{{candidateContact.name}}
	</option>
</select>

JavaScript

.directive( "ngSelectionChange", function( $compile ) {
		return function( $scope, $element, $attrs ) {

			jQuery( $element ).change( function( e ) {

				var target = jQuery( e.target );

				var datasourceKey = target.attr( "ng-datasource" );
				var datasource = $scope.$eval( datasourceKey);

				var actionKey = target.attr( "ng-selection-change" );
				var action = $scope.$eval( actionKey );

				var selectedIndex = target.prop( "selectedIndex" );
				var selectedItem = datasource[ selectedIndex ];

				action.call( $scope, selectedItem );
			});
		}
	})

UPDATE
I just stumbled upon the concept of using accessor’s in the directive scopes, that will help me get rid of the redundancy in the declaration of the datasource/iterator…
http://jsfiddle.net/ADukg/10/

UPDATE
I came across this directive when browsing the recently updated documentation system, this will do fine so there is no need to implement a ComboBox since the functionality is covered by the native select directive… http://docs.angularjs.org/api/angular.module.ng.$compileProvider.directive.select