Programming

Slow SPAs are worse than NoSPA

I got a digital subscription to the Economist for my birthday last month so I’ve started reading a lot more content on their site. As a result I’ve noticed a lot of weirdness with their page loads that was hardly noticeable when I was using the free tier of a few articles per week.

The site seems to be built as a SPA with a page shell that loads quite quickly but takes far longer to fill with content and which has some odd layout choices and occasional pops and content shifts.

The basic navigation between the current issue index and the articles is hampered by what appears to be a slow load or render phase. Essentially it is hard to know whether the click on a link or the back button has registered.

By replacing traditional page navigation the experience is actually worse. The site would be better if the effort going into the frontend went into faster page serving.

I’m not sure if the page is meant to be doing something clever with local storage for offline use but it seems to need to be connected when browsing so I’m assuming that this is something to do with the need for a subscription and payment gateway that prevents a fast server load of content.

It still feels as if the page and the 200 words or so should be public and CDN-cached with the remaining content of the article being loaded after page-load for subscribers.

The current solution feels like someone has put a lot of effort and thought into making someone that is actually worse than a conventional webpage and that seems a shame for a site with relatively little content that is mostly updated once a week.

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Programming, Software, Web Applications, Work

Prettier in anger

I’ve generally found linting to be a pretty horrible experience and Javascript/ES haven’t been any exception to the rule. One thing that I do agree with the Prettier project is that historically linters have tried to perform two tasks to mixed success: formatting code to conventions and performing static analysis.

Really only the latter is useful and the former is mostly wasted cycles except for dealing with language beginners and eccentrics.

Recently at work we adopted Prettier to avoid having to deal with things like line-lengths and space-based tab sizes. Running Prettier over the codebase left us with terrible-looking cramped two-space tabbed code but at least it was consistent.

However having started to live with Prettier I’ve been getting less satisfied with the way it works and Prettier ignore statements have been creeping into my code.

The biggest problem I have is that Prettier has managed its own specific type of scope creep out of the formatting space. It rewrites way too much code based on line-size limits and weird things like precedent rules in boolean statements. So for example if you have a list with only one entry and you want to place the single entry on a separate line to make it clear where you intend developers to extend the list Prettier will put the whole thing on a single line if it fits.

If you bracket a logical expression to help humans parse the meaning of the statements but the precedent rules mean that brackets are superfluous then Prettier removes them.

High-level code is primarily written for humans, I understand that the code is then transformed to make it run efficiently and all kinds of layers of indirection are stripped out at that point. Prettier isn’t a compiler though, it’s a formatter with ideas beyond its station.

Prettier has also benefited from the Facebook/React hype cycle so we, like others I suspect, are using it before it’s really ready. It hides behind the brand of being “opinionated” to avoid giving control over some of its behaviour to the user.

This makes using Prettier a kind of take it or leave it proposition. I’m personally in a leave it place but I don’t feel strongly enough to make an argument to remove from the work codebase. For me currently tell Prettier to ignore code, while an inaccurate expression of what I want it to do, is fine for now while another generation of Javascript tooling is produced.

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Programming

Google Cloud Functions

I managed to get onto the Google Cloud Functions (GCF) alpha so I’ve had a chance to experiment with it for a while. The functionality is now in beta and seems to be generally available.

GCF is a cloud functions, functions as a service, AWS Lambda competitor. However thanks to launching after Lambda it has the advantage of being able to refine the offering rather than cloning it.

The major difference between GCF and Lambda is that GCF allows functions to be bound to HTTP triggers trivially and exposes HTTPS endpoints almost without configuration. There’s no messing around with API Gateway here.

The best way I can describe the product is that it brings together the developer experience of App Engine with the on-demand model of Lambda.

Implementing a Cloud Function

The basic HTTP-triggered cloud function is based on Express request handling. Essentially the function is just a single handler. Therefore creating a new endpoint is trivial.

Dependencies are automagically handled by use of a package.json file in the root of the function code.

I haven’t really bothered with local testing, partly because I’ve been hobby-programming but also because each function is so dedicated the functionality should be trivial.

For JSON endpoints you write a module that takes input and generates a JSON-compatible object and test that. You then marshal the arguments in the Express handler and use the standard JSON response to send the result of the module call back to the user.

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Programming

Svelte – a first look

Rich Harris is a Javascript wizard who has already created the build tool Rollup and the framework Ractive. So therefore when he announced a new framework called Svelte I definitely wanted to take a look and see what problems he is trying to tackle with it.

Having spent some trivial time with some examples I have some understanding of what’s going on and how Svelte compares to other frameworks and approaches to building dynamic web pages.

One of the big things is that Svelte is based around a compiler that creates the deployed package which is just a variation on a Javascript file. So far I’ve found the compiler to be straight-forward and errors easy to understand. The compilation phase put Svelte closer to the Elm camp of pushing problems earlier in the development phase.

Svelte also offers a take on the Web Component, a Svelte component is responsible for managing its own dependencies and CSS. The definition of a Svelte component feels a little different to most component systems though. The basics of a templated piece of HTML is pretty standard but the component lives inside a HTML file that also uses the script and style tags to define the behaviour and appearance of the component respectively.

Using standard tags for this is, perhaps unsurprisingly, much more intuitive than defining React or Riot components.

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Blogging, Programming, Web Applications

An overview of Javascript reactive frameworks

This post is only meant to be a snapshot of the current state of the various DOM virtualising webframeworks that are around. I’m partly publishing it to try and discover more that I may not be aware of.

Many of these frameworks trace an ancestry back to Om and React. However each one tries to deal with perceived problems with the original frameworks. The most common being that React is too heavy and opinionated while not providing a consistent data model for components. Om on the other hand is in Clojurescript and therefore represents too much to learn in terms of a new language and build process.

Libraries

Most of the libraries build on a few common building blocks that I’m not going to elaborate on here. Virtualdom was an early attempt to separate the core idea of React from the rest of the library code. Virtualdom is only concerned with creating, manipulating and stringifying DOM structures in-memory. Browser DOM APIs involving linking to the actual rendered document so managing virtual DOM is more efficient and simpler because you’re not interacting with these underlying libraries.

ImmutableJS provides a Javascript-idiom interpretation of the Clojure data structures that Om uses (and which are available as the standalone library Mori).

Omniscient

The first interesting framework to discuss is Omniscient, which as its name suggests is heavily influenced by Om but is written in Javascript and therefore does not require you to learn Clojure to use the same techniques that Om uses. Omniscient is built on top of React and ImmutableJS and uses its own library Immstruct to add reference cursors to ImmutableJS structures. Reference cursors allow a component to observe and change sections of a data structure without having to manipulate the whole thing. So for example a component can be given a single sub-key in an object that represents its state and it cannot access or change anything that is not under that key. The code can also be simplified to behave as if the sub-key was actually just the whole data object.

Omniscient doesn’t suggest an alternative to Om’s CSP, instead providing a mechanism for passing event flow functions down the component tree. You’re free to choose your own event libraries. It also means that you’re free to make your own mistakes here as no guidance is really given as to how to structure your event scheme appropriately.

Omniscient is one of the earliest frameworks to re-implement Om and therefore has one of the better sets of documentation on its Github pages. That said there’s not a lot of documentation and the framework does not have a massive community. The situation is worse in most of the other frameworks though so this might tip you over in favour of Omniscient.

Ractive

This is a bit of a Guardian shout out as the primary developer Rich Harris is a Guardian interactive developer.

Ractive (Github) is a little be different from the other frameworks as you can essentially think of it as Mustache templates backed by Observables. You declare a data-binding and write templates in normal Mustache syntax but behind the scenes Ractive is driven by changes in the data and then writes new section of DOM in-memory according to what has changed rather than DOM diff’ing.

Also Ractive sticks with two-way databinding rather than unidirectional data flow so failures in synchronisation or rendering can be problematic.

If what you want to do is render content over a Javascript data model then there is a lot in Ractive that is very compelling. It uses templates with a standard syntax that is well understood and is a soup and nuts framework that sticks to core Javascript syntax and features. However if you want to use your own event or data model you are out of luck.

Mercury

Mercury on the other hand prides itself on modularity. A microframework it attempts to create a glue layer that allows other libraries to interact in a sensible and consistent way. The default components are Virtualdom and its own observer pattern to wrap state.

Mercury’s biggest problem right now is its lack of documentation. There is an expectation that you are going to read the source code to understand what the framework is doing and how to interact with the API. I frankly think this is unrealistic. The project doesn’t currently supply the incentive to do that. Unless you have a very particular desire to avoid any framework lock-in or you want to use a very specific combination of libraries that is not supported elsewhere its hard to understand why you would invest your effort here rather than in frameworks that offer more support.

Cycle

Cycle is similarly experimental, its biggest claim is that it is truly reactive and that the rendered page is purely the result of change in state. The introduction is couched in computer science theory but it would seem that at its heart Cycle wraps RxJS and Virtualdom in a glue layer that has the programmer writing the transform sequence between the event and the DOM structure.

I think it is a positive feature that Cycle re-uses a popular library to manage its state-transitions rather than implementing yet another custom version of the Observable pattern. It also makes the framework easier to get started with if you are familiar with the Rx.

Using established libraries also makes the lack of documentation more acceptable as the Cycle readme only needs to explain how the glue works in the framework.

As something built on reactivity you have to get used to dealing with intermediate state which can be bit difficult for the beginner.

Essentially any event where the user would expect feedback means you need write the conditional structure in the output. So if the user types a character in an input box then you need to write the value of the input box to be the characters the user has typed so far. Most frameworks work at a higher level of abstraction or rather they map closer to the DOM APIs, so getting a working application means grokking the way the dataflow works.

If you’re looking for purity (and a resulting simplicity in implementation) but not to have to learn a bespoke API Cycle is nicely positioned.

WebRx

WebRx is similarly built on top of RxJS Observables but is a much fuller-fat framework that is much more a spiritual successor to Knockout than owing much to the influence Om or React.

Rather like React WebRx doesn’t really provide generalised event handling but instead has special sauce bindings for DOM events and a MessageBus system built over Rx.

It is also written in Typescript and generally looks to play well within the Microsoft ecosystem. It’s interesting to me as an example of how different a language has to be before its regarded as a barrier. Clearly the use of Typescript means there are people who will refuse to use the framework regardless of whether it works for their use case. Other people are going to be attracted exactly because it uses Typescript.

Deku

Language choices are also interesting in Deku which is another attempt to re-implement React in a superficial way.

Deku makes use of ES6 and 7 features and doesn’t aim to support a broad range of browsers (unlike say Ractive). Again that is going to rule it out for some people but this is a more interesting as now we are within dialects of the same core language. Language choice for implementing frameworks is not straightforward. What are you looking for? Conciseness? Editor support?

Deku aims to take the dom diffing approach but avoid getting caught in React’s framework and approach. In particular components are defined just as Javascript objects rather that classes and instances. Something I think makes it more elegant that normal React Components.

It does however still use JSX which is quite interesting as the framework claims to be taking a functional approach but actually uses a DSL for all its DOM construction.

The lifecycle hooks are slightly different with more hooks for different stages of the process and Deku uses some interesting function passing to send changed data down the tree to components.

Deku doesn’t take much influence from Om though. It doesn’t have sophisticated event handling and uses mutable data with generous access and callbacks on data write to do re-renders. This means bugs and state issues are no less likely to happen than with any other framework. It does adopt the single atom idea with a single tree representing the app and the app renderer being bound to the body element.

As such if you like the idea of React but don’t want to bound into its concept of how a Component should be defined but do like JSX and trust the implementors to create a better dom diff than Facebook or Virtualdom, this is the project for you.

Conclusion

I’ve only chosen a handful of frameworks to look at here, mostly based on the ones I know, I’m expecting people to point out more in the comments. I also haven’t used all of these frameworks. Road-testing all of them would be a bigger task than just trying to describe the design choices they’ve made.

The most common pattern is to try and improve the rendering time versus React by using different virtual dom difference algorithms. Usually this is combined with Observed variables that provide a Reactive component that allows changes in the data model to be conveyed to the DOM model with no coding required.

Few of the frameworks engage with the functional reactive programming paradigm by building abstract event streams or indeed any abstraction over discrete events.

The idea that the app should be a single data structure that represents the whole page seems to be gaining significant traction with several of the frameworks recommending this as an approach.

The explosion of frameworks resulting from the release of React is, I think, a positive thing. Initially it seems really daunting that you have all these choices but when you look at the real level of difference between them you can see that they are actually quite tightly coupled around a few common and core ideas and that mostly they express differences about the concerns that a framework should have which feeds into the wider conversation about micro or comprehensive frameworks.

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Clojure, Programming

Creating Javascript with Clojure

This post is an accompaniment to my lightning talk at Clojure Exchange 2014 and is primarily a summary with lots of links to the libraries and technologies mentioned in the presentation.

The first step is to to use Wisp a compiler that can turn a Clojure syntax into pure Javascript, with no dependencies. Wisp will translate some Clojure idioms into Javascript but does not contain anything from the core libraries including sequence handling. Your code must work as Javascript.

One really interesting thing about Wisp is that it supports macros and therefore can support semantic pipelining with the threading macros. Function composition solved!

If you want the core library functionality the logical thing to add in next is a dependency on Mori which will add in data structures and all the sequence library functions you are used to with a static invocation style that is closer to Clojure syntax.

At this point you have an effective Clojure coding setup that uses pure Javascript and requires a 50 to 60K download.

However you can go further. One alternative to Mori is ImmutableJS which uses the JavaScript interfaces (object methods) for Array and Map. If you use ImmutableJS you can also make use of a framework called Omniscient that allows you develop ReactJS applications in the same way you do in Om.

ImmutableJS can also be used by TransducersJS to get faster sequence operations so either library can be a strong choice.

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Programming

Clojurescript at London FunctionalJS

At the January’s London FunctionalJS meetup the technology under discussion and use was Clojurescript. There was an introduction to the language basics from Thomas Kristensen of Forward, which was really much more about the basics of the syntax. We then went into the dojo exercises: the choices were implementing the Todo list SPA (the Javascript world’s Pet Store), using Clojurescript with an existing Javascript framework people were already used to working with or doing some 4Clojure.

Everyone ended up doing the Todo list which is interesting in its own way. Clearly the SPA is seen as the benchmark for evaluating these kinds of technologies.

Most of the teams were able to get the basic Todo functionality done in terms of adding and removing things from the list and re-rendering it. Most teams seemed to abstract the rendering but most put the list management into the callback for the event.

Again I was interested to see that most people grasped the idea of an atom and were able to manipulate its value. Because that kind of stuff is second-nature to me now I was wondering if it would cause issue in terms of creating a modifying function rather than directly manipulating the value. The example in the setup functions of the dojo code using conj seemed to be straight-forward enough for everyone.

Identifying and deleting items seemed more problematic. Some people wanted to do it by index but for the most part matching the text of the todo-item seemed to be popular. Probably the sensible way to actually manage the items is to uuid the items to allow their underlying state to change away from the identity.

Laziness definitely caught people out, including myself! I’ve moaned about the fact that using map purely for side-effects in fact results in the form not executing. Despite this I fell into the trap again, however fortunately having encountered it before I could reverse into a quick doall.

Other teams imaginatively re-implemented doall using loop. Which I guess is testament to how easy it is to do things in a LISP.

One thing that was hellish in our team’s code and which I think cropped up in the other teams as well was the amount of set! we were applying to build up very low-level DOM calls. Right at the end I remembered that Google Closure was available to abstract some of that work away. However it still means that your knowledge of Clojure needs to be heavily supplemented by low-level DOM APIs as well as what is available in the Google Closure library (which is not the best known of libraries).

I was also wondering whether doto might not have cleaned up our code a lot. It’s an issue that a lot of Javascript mutable state is not easy to wrangle with things like threading macros that normally ease the pain. I’ve seen this in the WebGL dojos as well.

The final ugly issue of the evening was the project template that managed to both run on my machine and not run on my machine. The template was more complex that the standard SPA template as it used Compojure and Clojurescript (presumably using the former to serve static assets on localhost). Leiningen skeleton projects have to work and be reliable, otherwise potential adopters just get frustrated and quit.

The reactions were interesting, a guy on our team at the end asked why he would want to use Clojurescript. Good question. People who were doing things like building HTML5 games seemed to see the potential and advantage much more. This is an area I hadn’t really considered before but it does make a lot of sense as regular Clojure has already had a lot of success in implementing animation and complex state machines.

For me the alternating between high-level Clojure and low-level DOM APIs was painful. I’m going to be more interested in having wrappers that allow high-level programming consistently in a project. And I am going to be thinking about games more!

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