Why pure JavaScript web apps are neither the future nor a good idea

06 Jun 2020 - tsp
Last update 05 Jul 2020
Reading time 27 mins

Note: This is an opinion article on the future of web development. Currently there is a trend about building more and more logic into the client - even for simple tasks. That trend has been there previously and it has been a bad idea back then. This article tried to present a few arguments why I don’t think that this is or should be the future of the web.

Note that - if you expect that - I won’t tell you that JavaScript is useless or that frameworks like Angular or React are bad - note that react is a bad example though since it supports complete server side rendering without any client JS support if used correctly though. They solve a particular problem and they’re great at this (I’ve had the opportunity to work with both of them and with different JS environments). But they’re often used in a wrong or bad way - most of the time to be precise.

This article has been inspired by a friend linking me to an article about backend-less JavaScript applications.

As usual this article might be extended in case of more ideas coming to my mind or getting external feedback.


Everyone who does web development full- or part time knows it. There currently is (again) a trend to develop websites and basic web applications - not speaking about desktop applications running in the browser though, more on that later - that are running as massive JavaScript client side applications inside the browser. They do not simply provide some features that are only supported using JavaScript and they do not only enhance their functionality using JavaScript but are completely composed on the client side using a massive amount of JavaScript code that fetches information from distributed sets for APIs that might even be operated by a huge amount of different backend providers. They take the idea of creating mashups to the next level.

Just as a short summary as not everyone will reach the end of this article - the main features that the web offers in my opinion are:

But first let’s look at some history of computing and the web.

A little bit of history

Basically first it all started before the web with having some big mainframe computers and a number of remote dumb terminals. The terminals just had been capable of displaying or printing out data, all computations have been made at the mainframe centrally. This has been done that way since computational power and storage have been pretty expensive and took up way much more room than one can imagine today. A hard-disk that could store an megabyte of data filled the space an refrigerator did today and a computer with the calculation power of and today’s smartwatch would have filled a whole building, required massive electric and cooling infrastructure and planning and was error-prone to a huge set of errors starting from being interrupted by static electricity up to bugs crawling into the machine - which they liked because of the higher temperature - and causing shorts inside the circuits. Funnily the word bug naming an error originates exactly from this behavior.

Note that the Internet was already in existence at that time - the internet started at 1st January 1983 with the adoption of TCP/IP for ARPANET. All of the core features that are now holding the Internet together have been developed back then - the core features of the network have been it’s decentrality and robustness as well as easy expansion. Features that are in place still of today even if there is every few years someone who proposes to exchange that infrastructure for a centralized “modern” approach which fortunately never happens.

So back in the 1970 to 1980 we had a scenario that one could describe as having a smart server and dumb clients.

Then the time of personal computers started in the 1980. Computational power and storage became more cheap and more compact. Computers moved into the households - at the beginning they’ve been a nice toy for geeks but starting with the x86 architecture - that we still use today - and especially the 80386 in the year 1985 the personal computer gained way more computational power and an major 32 bit computational environment. On the other hand communication over long distances was rather expensive and slow - since the 80s there existed dial up network connections with speeds of about 40 kBit per second - so that’s about a factor 1000 to 10000 slower than the internet connections used by many people today. The first commercial dial-up connections started in the early 1990’s and people started to build the web on top of the Internet during that time.

The web started to be a simple idea of being a global information medium on which people are capable of hosting their HTML documents that provide easy and standardized, human readable markup that can be rendered by a browser that provide metadata and link between each other. The concept goes back to the 1946 but was - in it’s today’s form - proposed 1989 by Tim Berners-Lee who also implemented the first webserver speaking HTTP, the specification for the HTML markup language and the first browser which also supported editing directly inside the browser in 1990 at CERN. In 1991 the server went online and was reachable for everyone on the web. Note that the first webbrowser supported a feature that most of the time is hacked into today’s webpages by using a huge bunch of server-side and client side code - it allowed direct editing of webpages. You could simply point your cursor somewhere in the webpage, edit it’s content like you’re editing in a word processor and then - if you had the FTP permissions - upload the document via either FTP or an HTTP PUT request to the webserver (HTTP PUT being a supported method in modern HTTP even if still not widely used or sometimes used in a different way to upload information to backend APIs in REST patterns).

Webpages have been rather simple and just have been rendered by the browser. So they contained just some dumb markup. Servers have been rather dumb and only delivered the data. So the web has been a little less interactive than one would imagine today. Applications ran as native code on the client side (like most programs still do today). During the same time stuff like transferring files using FTP and discussions in Usenet using NNTP have still been the way to be interactive on the web.

So back in the 1990’s we had a scenario that one could describe as having a dumb only file-serving server and smarter clients (but nearly no interactivity on the web; running local applications).

The main advantages of the web that one can still have today have been:

Soon after the emergence of the Windows operating system and ActiveX in 1996 the idea emerged to host ActiveX components inside the browser - namely inside Internet Explorer. Note that ActiveX is an API that has been built for componization of applications - the basic idea back that still lives today in many popular office suites was that a document can be composed of components from different applications like for example the ability to embed a spreadsheet into a word processor without the word processing having any knowledge about spreadsheets. This has been done by launching an spreadsheet processing component in the background - which is the ActiveX/OLE component and rendering it’s result inside the word processor who only knows that it has to launch a component of a given type. The same idea expanded to the web - including the ability to download components. This allowed on to download whole applications into the browser, support interactive forms and database access and animations. Other technologies that emerged at a similar time had been Java applets, Flash animations and applications and some other browser addons.

Logic moved to the browser with all it’s side effects: Not all browsers supported this rather complex logic, one had to install extensions that have been just available for some platforms so the portability of the web got lost. On the other hand most platforms had - because of their complexity - massive security problems so malware targeting users machines by this mechanisms emerged. The higher demand on calculation power as well as memory on client machines did the rest and so these technologies did not really survive long outside of some specific bubbles like flash games or some Java applet based remote interfaces for machines or telephony exchanges.

To counter that server side scripting and programming emerged. First there has been CGI that simply instructed an webserver to execute an arbitrary binary or script in case a web request has been made to a specific address - so the webserver got something like the inetd daemon that just launched applications on demand, passed request information and passed returned information from the application towards the browser, wrapping it inside HTML. The most accessible way when using CGI back then for the average user has been to use Perl scripts - which was and still is somewhat a hassle to program with even if there are really potent and powerful string functions supported compared with many other languages. Then PHP emerged. This language simply looked like a hack but it allowed mixing HTML markup and code inside the same file which made thinking about and building pages much easier. PHP has been the language of choice for every hobbyist web developer who wanted to add interactivity on his site, later on paired with the MySQL database system. Interaction with webpages followed a strict request-response pattern normally using either links for non state-changing GET requests as well as forms that could pass selected options and content of text fields and areas to the server site using potentially state changing POST requests. After every action triggered by the browser data got sent to the server, the server processed the request and returned new information towards the client.

If one for example would’ve implemented a simple solver for linear equations one would provide a nice input form for the user. After the user has filled the form he’d transmit the form to the server. The server then would perform input validation - in case of an error he’d return a error message to the user and potentially allow correction of the input or he’d perform the calculation and return the result. Each and every request of course would require a complete page reload which is not much of a problem for simple page designs but in case there are some complex layouts that was still somewhat feeling clumsy for some users - especially on slow connections.

One had again a smart server - doing computations - and mostly dumb client - doing only the display - situation as back in mainframe times. On the other hand the main advantage was that one also had the server as a gatekeeper into internal databases and internal state so this is also (still) the area in which one is validating user input, managing most of the access permissions, etc.

To give users a more fluid feel JavaScript emerged. This is not to be confused as it was in the early days with Java. Java applets run full blown bytecode inside the browser and can perform major computations. JavaScript is capable of this today too but was a rather inefficient and slow programming language back then. It allowed to run easy scripts in addition to previous server side architecture. For example one could intercept the submission of forms to the server, perform some input parameter validation on the client and do quick and fast user feedback in case of errors before submitting the values. One had to to server side checking though since code running on a client can never be trusted. Sometimes one could even perform the calculations on the client side if one also provided a fallback in case JS was not supported.

From this on pure JS applications emerged that simply left out the server side fallback. Clients that don’t support JavaScript or have them not enabled due to resource or security constraints are not capable of running such applications though. This went further and further and some of the drawbacks will be mentioned later on (since this post is exactly about that topic). On top of that asynchronous script driven communication channels as asynchronous XML HTTP requests (AJAX) as well as WebSockets and WebRTC data channels emerged. They’re often used to load information from a variety of backend services or peer to peer connections like on has done from native client applications. They try to provide a fluid view of applications. That’s the state of today. With logic moving into the browser one could see this as:

Having a smart client and a rather dumb or mixed server again, but relying on a rather error less and high bandwidth internet connection since one loads the application and data over the network on demand.

So a short summary to show the effect I’ve always been fascinated with:

Some problems

Now what’s the problem I see with this approach?

Requiring JS support on the client (Inconsistency, Security)

This might sound rather basic but the main problem is that JavaScript support is required on the client side. With HTML there is a rather simple specification of a markup language out there that can be implemented in a few days to weeks by anyone who’s capable of writing a parser. Up to HTML 4.01 it was clearly specified what’s valid and one could simply reject and invalid and non conforming code (that changed with HTML5 because of the huge amount of erroneous webpages out there - in my opinion that’s a bad idea since webpages should simply just use standards conforming markup but that was driven by the market of having browsers that just try to show more than their competitors and started of doing sniffing and guessing how something should be interpreted). On top of that simple HTML one could - but didn’t has to - add rather simple property based layout rules that are specified in cascading stylesheets. They provide clear and simple fallback methods in case something is not supported, allow client side tailoring and adding user stylesheets to adjust rendering to one’s personal preferences - that’s a feature often forgotten by webdesigners today but it’s still there. The main point with this is that every browser can simply implement HTML and is capable of viewing and interpreting a webpage correctly. There is no need to target a specific browser or a specific version of a browser. A webpage that works with Internet Explorer or Google Chrome also works with textmode browsers like Lynx or Links as long as it’s conforming to the standard. It might look different and one has to follow accessibility standards but it simply works. And webpages can be processed automatically.

On the other hand JavaScript - or let’s say ECMA script - is a rapidly developing language that gets new releases every few years with a huge set of APIs supported by a variety of environments - different DOM manipulation strategies, a huge amount of data storage technologies like structured WebSQL or unstructured key-value stores, a huge amount of graphics processing APIs like 2D and 3D canvas, optional APIs that allow background processing like web workers. This is all stuff that’s not specified in a centralized way and that’s not implemented in a few weeks, not even in a year when developing from scratch. This set of rapidly developing APIs is evolving and requires a huge amount of feature detection and would require massive fallbacks if one doesn’t want to target a specific browser. Because of this it’s way more common to hear sentences like “this application is only supported on new versions of Google Chrome or Mozilla Firefox” or similar. So we’re back at only supporting given versions of given browsers - these webpages will not be runable in 10 years on browser that have evolved further without major refactoring and modifications. And they’ll for sure not be runable in fifty years from now - webpages from the early 1990s are still displayable by browsers today on the other hand.

Funnily many applications do not even correctly detect all features they require but simply fail in some unpredicted way in case something is missing or in case some API has evolved.

The huge complexity on the other hand opens up a huge number of potential and already found security problems. There is one problem after each other which leads to JavaScript being disables in security sensitive environments. There are even security holes that are hardware based that one can exploit using JavaScript such as cache timing sidechannels and rowhammer attacks.

JS being a huge resource hog

JavaScript is one of the most resource intensive and inefficient runtime environments on the market today. Try it yourself - launch a browser and open a few hundred tabs of a plain HTML webpage and of a JS webpage on the other hand. If this doesn’t really convince you keep them open and watch memory grow due to data continuously loaded and especially also due to external memory fragmentation on the JS heap. This is another reason why many people have to restart their browsers periodically or simply disable JavaScript for longer battery life.

Load times

JavaScript applications tend to consist of many libraries and a huge amount of code to realize their logic. This has to be loaded on demand at least on the first visit of the webpage and then after each change or after each cache timeout. JavaScript can only partially be loaded in an asynchronous fashion - HTML on the other hand can be displayed incrementally even when loading really huge documents even before everything has been loaded.

When loading multi megabytes of JS libraries this might be a huge problem over high latency and low bandwidth links - it takes time to download all resources associated with an JS application, it takes time to interpret and compile the code, then it takes time to load the data asynchronously that should be displayed to a user. And on every asynchronous load a high loss link might fail and trigger a retry or load failure. Loading times are - in contrast to the expectation - for the initial load normally way higher than for plain HTML and server side logic solutions.

Just beware that any single load or request may fail and might need a retry. And that every single load over a low bandwidth connection takes much time.

Complex failure modes

Since many scripts tend to load data not only from a centralized source but from a variety of APIs - many times even operated by a huge amount of different providers like suggested in some articles on pure JavaScript web applications - the number of components that might fail, might be refactored or might be organizationally changed drastically increases. One has to handle each and every failure mode on the client side. There is also no single gatekeeper to one’s backend any more - the client has to know each backend service and in case on modifies an API one has to support multiple API versions at the same time since cached script versions are still out there that perform requests the old style - sometimes for a longer period of multiple hours to days or weeks. The typical solution is simply break existing instances and expect frustrated users to reload their pages.

Distributed backends

What does it mean to distribute your backends onto multiple different service providers? It means that you:

You have to perform access control on each backend service. Basically this is an approach that I somewhat like since I also try to perform access control additionally using the users identity at all backend services that I call out from my webservers. But on the other hand you loose this additional gate keeping point that can do at least some input parameter validation and will normally only produce internal specific requests - although your services should be hardened of course.

User script intervention

This is also something one simply forgets. It’s always possible that users inject their own JavaScript as userscript or Greasemonkey script libraries into a web context. This is also often done using browser extensions. One cannot simply trust the users environment to work in a consistent way. Sometimes these scripts do interfere and it’s nearly impossible to effectively debug such failures and error modes.

Less major development tools

Of course there is an advance in technology that one currently sees such as more major languages such as TypeScript. But on the other hand native and server side application development offers just a huge bunch of major tools. This starts with static analysis, compile time error detection, being capable of doing intensive unit tests, etc. As I’ve written before there are some advances in languages such as TypeScript and having automated testing tools such as Selenium available - but it’ll be a long road till they reach the maturity level of existing tools for server side languages such as Java and even PHP.

This of course leads to less error-resistant code being in existence - and since there is this idea of fast changing web the error rate within web applications is just larger than in most other areas. This combined with the previously mentioned inconsistent environments makes developing client based applications way more error prone and hard to debug than any other environment.

Non archivability

This is a major problem I see with JavaScript driven applications. In the early days you could simply save a plain HTML webpage and reopen it offline a few centuries from this moment on. If you try this with a JavaScript driven webpage that gets build by querying a huge pile of backend APIs doing AJAX requests or WebSocket exchanges - there is nearly zero chance that you can display anything ten years from now. You’re simply not capable of saving a document in a given state and archiving it. This is a bigger problem than one might imagine on the first hand - think about libraries not being capable of archiving knowledge on books or papyrus for example.

Non bookmarkability

This is just a small extension of the previous point. Have you ever tried to bookmark a typical modern JavaScript driven website in a given state and reload it a month later? In nearly all cases you do not get back to the same state as before. There are some hackish ways of applications that try to achieve that but they are neither reliable - because they rely again on some inconsistent presence of some features - and they still break archivability.

The way I like to develop applications (The solution to most problems presented above)

I basically think of JavaScript of providing added value for responsive webpages on top of existing technology. In my opinion an web application (with some rare exception that I’ll mention at the end) just has to work without any client side scripting. Yes, that means having trip around times for requests, form submissions and no more interactivity. It means having no nice editors, no WYSIWY(M)G editing of content, no client side value pickers and so on. But it means that every browser in existence is capable of using ones service. And on top of that it’s nice to add JavaScript features that make stuff more responsible - like loading additional content via JS instead of paging, continuously updating content to reflect the current state, loading partial content via a backend request, animating graphics, providing WYSIWY(M)Q editing features that hides markup from users and so one. It might even allow some additional features like image manipulation on the client - in addition to the basic core features exposed via a server side service.

This allows:

On the other hand there is some JavaScript centric application type that I also expect to require JavaScript inside a browser. That’s the type of application that projects like emscripten and webassembly have been developed for - for example one can run complete CAD applications inside the browser, complete image manipulation applications or even computer games - without having to install them. Of course there is this major drawback of security but since these are applications that are comparable to applications that have been installed the only drawback from this point of view is the update-ability by simply exchanging server side resources. Such applications of course have to use extensive client side features. Some examples for such applications might be:

In my opinion each and every website whose main objective is to present information just has to work without any scripting at all. If the main objective is to substitute and desktop application on the other hand the required scripting is of course alright. But this is not the case for a simple database frontend or for example a reporting application in my opinion. This has nothing to do with a modern or antique approach - it has something to do with keeping up the most basic properties of the web:


Please again keep in mind that this is an opinion based article and everyone might have a different one.

This article is tagged:

Data protection policy

Dipl.-Ing. Thomas Spielauer, Wien (webcomplains389t48957@tspi.at)

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