Welcome!

Weblogic Authors: Yeshim Deniz, Elizabeth White, Michael Meiner, Michael Bushong, Avi Rosenthal

Related Topics: Machine Learning , Java IoT, Adobe Flex, AJAXWorld RIA Conference & Expo, Agile Computing, Apache

Machine Learning : Article

Event-Driven Web Application Design

"The era of boring web sites is over !"

A Problem of Approach

The sad truth now is that both approaches often lead to hard-to-maintain products that don’t scale gracefully and are a pain to make accessible, localise to different languages or customise to different needs and channels. This is caused by false assumptions made by practitioners of both approaches:

  • The framework approach relies on a silver bullet and approaches web development with fat-client application ideals from higher programming languages like Java or C++. This does not take into consideration the fact that web development is a discipline that operates with great uncertainties regarding the nature of client-side hardware and software. Optimization has to be for the user and not for the developer (although these don’t necessarily have to be mutually exclusive).
  • The web standards approach would not be a problem at all if people would follow standards with the goal of making things easier by following an agreed approach and not see following the words of the W3C to the last detail as the only way to do things. Web standards are there to take the randomness out of web development and not to act as a policing tool.

The crux of the matter is that we don’t really yet understand how to build a real web application. We take tried and true methodologies that cover other development scenarios and try to shoe-horn them into something that helps us to achieve what we want on-time and within budget (and when was the last time that happened?).

The other problem is that we approach web application design with browser limitations in mind and plan only for what browsers can do rather than what the application should offer the user.

When it boils down to it, the main differentiator of a web application and a web site is that an app has much more interaction and is process-focused rather than content-driven. Users come in to achieve a goal: They provide data to the application, they use the application to enhance that data, and then they expect data to come out. They interact with components of the application and expect them to do something that brings them closer to their goal. It is of utmost importance that we plan for how users interact with the product and react accordingly.

When trying to accomplish this in the browser, there is one core technique at our disposal: Event handling.

Understanding Events

We must try to understand what an event is when it comes to user interaction through the duration of a user session.

Events as defined by the W3C are very complex and can be tough to understand. However, the most common way of thinking about events in JavaScript is:

  • Something happens to an element, to the main document, or to the browser window and that event triggers a reaction. For example, the window finishes loading and on that event we start an initialization method; or the user clicks a link and we use that event to trigger another function.

Most framework-generated code or even handcoded methods use this kind of event handling. We take the window, or a certain element and add handlers defining the event that should trigger a function. This leads to a rigid relationship between the markup and the functionality. As the interface of a web application might change (more links in a component, other buttons, more complex forms) this need to add more cruft begins to cripple our applications. It also means that maintenance must happen in two places — a change to our HTML means that our JavaScript needs to change, too.

The DOM Event Model however goes a bit further. It has a more granular definition of the workflow:

  • Something happens; an event occurs.
  • The investigation begins what element was activated and how. This happens by questioning each element from the window to the body to the first child node and so on until the element that was activated, the event target, is reached. This is called event capturing.
  • When the element is reached, the process of reporting goes back up through the DOM right back up to the window. This is called event bubbling.
  • You can intercept events on both legs of this journey at any time by adding event listeners to either the window or any of the objects that get queried. Event listeners define what event to look out for (click, keypress, load, mousedown…), the object to which the handler should be applied, and what method to call when it happens.
  • You can stop events from going back up to the window by calling a cancelEvent() method and you can retrieve the object the event occurred on, the event target, with a helper method called getTarget().
  • You can add as many listeners waiting for as many different events and each calling as many methods as you like.

Understanding and implementing this event model can free your application from the constraints of defined elements. For example, instead of applying an event listener for each link in a menu, you can assign a single listener to the menu item itself and retrieve the event target. That way you don’t need to change your script when the menu gets larger or when links get removed from it.

This is a very powerful and flexible approach often referred to as event delegation. Event delegation allows you to react to changes in the document while applying fewer event listeners. You can assign different handlers to different parts of your document (the menu, the main content, a sidebar, a language change menu) and define methods for each event (was it clicked? was a key pressed on it?). These methods then retrieve the element that was affected and react accordingly; for example, you can react differently for links versus buttons.

When using this idea (waiting for an event, investigating where it happens and acting accordingly) in web applications we mostly confine ourselves to what the browser reports us — the DOM events. This is not really necessary, and it’s a big limitation. Much that happens in an application — like a user switching between tabs in a TabView Control — could be thought of as an event and dealt with in the same manner.


More Stories By Christian Heilmann

Christian Heilmann is the author of 'Beginning JavaScript with DOM Scripting and AJAX' and he contributed a chapter on accessible JavaScript to Web Accessibility: Web Standards and Regulatory Compliance. He has worked in web development for almost 9 years for several agencies and .coms, is currently a lead developer at Yahoo! in England. Chris blogs at http://wait-till-i.com.

Comments (1) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
riccardo molti 11/21/07 08:08:38 AM EST

So web developers are now 'Front-end engineers' - I like it! Let em start looking at Yahoo! UI, sounds cool.

@ThingsExpo Stories
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
It is of utmost importance for the future success of WebRTC to ensure that interoperability is operational between web browsers and any WebRTC-compliant client. To be guaranteed as operational and effective, interoperability must be tested extensively by establishing WebRTC data and media connections between different web browsers running on different devices and operating systems. In his session at WebRTC Summit at @ThingsExpo, Dr. Alex Gouaillard, CEO and Founder of CoSMo Software, presented ...
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, introduced two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a multip...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
SYS-CON Events announced today that Evatronix will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics gr...