After learning all the ways an Angular web app can perform HTTP communication, I have a better understanding more of Angular’s “Tour of Heroes” tutorial app. And even better, I have a better idea of how I could write unit tests for it! That wasn’t something covered by the tutorial itself, so writing tests for the tutorial app is my self-assigned extracurricular activity. This follows my previous self-assigned homework, an aesthetic overhaul using Angular Material component library.

An Angular project created via “ng new” command sets up a unit testing pipeline and a few boilerplate tests. “Tour of Heroes” was created this way but it was never touched in the tutorial. Every time we call “ng create” to add a component, that boilerplate also added a simple test to verify that component could be created in the test framework. By the end of the tutorial, we have a handful of these simple creation tests. Most of which would fail, because those components have become more complex than the original boilerplate and the test hasn’t been updated to match.

Import Dependencies

First step was to import all the missing dependencies so a component can even be created in the test harness. I first did this mostly by searching for error messages and copying the answers, but it was an unsatisfying approach because I didn’t understand what I was doing. To address this, I paused my mindless copy/paste and started studying. I started with Angular Developer Guide to Testing which led to my reactive programming tangent with RxJS. Now I’m back, and I understand how to use import section of TestBed.configureTestingModule to bring in dependencies needed by component under test.

HttpClientModule to HttpClientTestingModule

Once components could be created, I was faced with a long list of HTTP failures. They all had the same cause: components that need to perform HTTP communication imported HttpClientModule, which tried to make actual HTTP calls to a server that isn’t online. For unit tests, we need to use HttpClientTestingModule to redirect component HTTP activity to behavior controlled by unit test infrastructure.

Mock Services and overrideComponent

Once tests were in place for services that used HTTP directly, errors came from components that indirectly used HTTP via those services. To keep tests small (the whole point of unit tests) I stubbed out those services with mockups that had just enough behavior to support specific unit tests and no more. Hooking them into the system required using overrideComponent to switch out real services for their simpler mockups.

For my first pass, I wrote mockups directly as TypeScript classes. This is a simpler and more direct first pass, but I think I’m supposed to use “Spy” mechanism provided by Jasmine testing framework for such mockups. Learning to use Spy is still on the to-do list.

Code Coverage Report

Running “ng test –code-coverage” activates code coverage report courtesy of Istanbul. A brief coverage summary is printed to console every time the test suite is executed, but I wanted more details to see where I need to focus my effort. The detailed report is in HTML format under the /coverage/ subdirectory. I’m supposed to go double-click on that file to bring it up in a web browser, but I’m running Angular inside a VSCode Dev Container and I can’t “just” go and double-click that file as it is not accessible to my local web browser.

Solution: quickly whip up a static file web server with the serve-static package, letting my local web browser access the report via a port opened on my dev container. I added that file along with a shortcut to my packages.json file so I can bring it up by running “npm run coverage.”

100% Is Not 100%

=============================== Coverage summary ===============================
Statements   : 100% ( 82/82 )
Branches     : 100% ( 7/7 )
Functions    : 100% ( 47/47 )
Lines        : 100% ( 75/75 )
================================================================================

These mechanisms helped me to write unit tests that exercised all code paths: 100% code coverage! But this metric is misleading, because there’s much more to an Angular app than its TypeScript code.

Many important pieces of functionality live within HTML templates and are not covered by code coverage statistics. That requires accessing ComponentFixture.nativeElement. From there we can navigate the DOM tree, query for elements, and verify they are expected.

There’s much more to Angular testing. I haven’t even gotten into other things like verifying Angular router functionality but I am getting tired of Tour of Heroes. Time for a change of pace.

A working understanding of reactive programming with RxJS Observables for Angular was listed as a prerequisite to Angular guide for HTTP client. After my long and convoluted tangent to learn RxJS, I felt I was finally ready to dive in and learn how to apply RxJS to handle HTTP transactions in an Angular web application.

One of the most powerful aspects of RxJS is the declaration of an Observable pipeline is a template. It means we can set one up independently of using them. To use them we call subscribe(), and it is a template that we can reuse by calling subscribe() again. An unexpected downside of this power is that nothing actually happens until we call subscribe(), which can be counterintuitive when we use the Angular HTTP client for operations like DELETE. Outside of Angular/RxJS, such things are fire-and-forget but here we have to subscribe() to start things in motion even if we don’t really care about the results of that subscription. This is apparently a common mistake because it is called out multiple times on this page. I also remember seeing this in the “Tour of Heroes” tutorial, which was absolutely wild when I first saw it. I now understand why it behaves that way, but I still think it is weird.

Unrelated to RxJS, I thought “Requesting a typed response” section was interesting. It enables TypeScript compile-time checking, which helps keep our code straight, but we have to remember we’re still on the hook for runtime checking. Sanitizing data is important for security! This also explains why the example code would copy elements from the result and not blindly copy the whole object. Blind copy would leave our code vulnerable to a maliciously written object that comes with its own toString() or something that is likely to get called in the context (and authority!) of our application code.

With my current basic understanding of RxJS and HTTP, the first half of this page was fairly straightforward. Then things got weird with “interceptors”. I understand it is a very powerful concept that allows separation of concerns across different chunks of code, each handling an aspect of HTTP activity. But getting them to all play nicely together seems to be a challenging task with lots of room for error. A very powerful gun aimed at our feet, it seems.

Even just loading them up has pitfalls. There’s a recommendation to load them with a “barrel” but I haven’t understood the tradeoffs to use/not use them. I also understood that load order mattered, but it didn’t cover symptoms of getting the order wrong. There’s even a back channel for application code to control interceptors (passing metadata) via HttpContextToken object.

An application of interceptor that looked very impressive was the ability to return a cached value immediately while also issuing the HTTP request. Then the real updated live value from the server is given, all on the same Observable! This is something that would have been really complicated to do with plain JavaScript Promise (async/await) and the first real “A-ha” for me to see power of RxJS in action.

Interceptors are also how Angular performs client-side work to protect against cross-site request forgery (XSRF) adding an XSRF-TOKEN in the header. It’s only part of the solution, though. It needs to mesh with server-side code to set the token and verify the token. It is on my “To-Do” list to find an implementation example, probably with Express.

And finally, there’s a section on using HTTP client in unit tests. This is the section I can put to work immediately.

I went on a reactive programming tangent thinking it would help me become an effective user of Angular web application framework. Because some very important parts of Angular made extensive use of a JavaScript reactive programming library called RxJS. I found a lot of general information about reactive programming out there, but I need to stay focused on Angular. Returning to Angular documentation, I picked another developer guide section to start reading: “HTTP client“. This page has a “Prerequisites” section at the top which linked to an “Observables & RxJS Guide“.

It was an introduction to reactive programming with the RxJS library, with examples that are relevant to Angular apps. I didn’t know this guide existed. If I had, I would have started here first! If I had, I still wouldn’t have understood RxJS immediately, but I would at least have a better focus as I ventured to other RxJS guides. Mostly thanks to Observables in Angular which showed the most common RxJS usage patterns.

I was mildly disappointed the Practical Usage page had only two examples, and one of them was the type-ahead autocomplete mechanism already covered in Tour of Heroes. At least that one had a breakdown of how the asynchronous processing pipeline worked to accomplish its goal. The other example “Exponential backoff” had no such explanation. Just an overly optimistic claim “With observables, it is very easy” before we were tossed a chunk of code with no comments nor a breakdown of what it did. Definitely room for improvement here.

RxJS Observables were compared & contrasted against JavaScript Promises in the “Observables compared to other techniques” section. I saw some unavoidable overlap with similar topics on other resources I recently read but still, it was a great way to help my brain think about how to make use of RxJS aligned with its strengths. But I know the best way to get comfortable with RxJS is to start working on code that use it.

I learned a lot from reading Angular’s Developer Guide to Testing, one of which is that I have a significant weak spot in my Angular understanding: how and when to use RxJS for asynchronous operations. Not just for testing, but also for writing Angular application code. On my first run through “Tour of Heroes” tutorial, RxJS was a black box I didn’t understand at all. On my second run, I understood the tutorial enough to understand specific uses of RxJS from context, but my understanding did not extend to the rest of that library. I certainly don’t know how to employ RxJS for my own tasks. It’s time to buckle down and read official RxJS documentation.

This was quite a chore. It appears RxJS official documentation was written by its development team for an audience that already knows what it does and why they would want it. It started with “RxJS is a library for composing asynchronous and event-based programs by using observable sequences” and jargon gets thicker from there. (Interspersed with words like “just” and “simply” which this beginner found ridiculous.) There was no “Getting Started” section. The next-best candidate section “Installation” is full of material telling existing users how to migrate breaking changes, not an introduction to new users.

The good news is that, as of this writing, RxJS is still under active development. Today’s stable release 7.8.0 has a timestamp only a few weeks old. (December 15th, 2022.) I was concerned about that, because RxJS was a solution for JavaScript asynchronous programming before JavaScript evolved to have its own asynchronous constructs like async/await. It doesn’t map cleanly to Promises and conversion is a bit of a mess. But RxJS still does things that standard JavaScript doesn’t do, so there are still scenarios where RxJS would be the right tool for the job. It’ll take more learning before I recognize those scenarios.

Observable: RxJS foundation class. One thing that demystified a lot was rewriting an analogy using plain JavaScript. Seeing something familiar and understandable (with my very recent JavaScript education) gave me a starting point to try understanding the rest of the page. Unhelpfully this was at the bottom of the page.

Observer: It took a while for me to understand observer where my code fits into the system and I can use as little or as much of it as I need for a scenario. It can be a single callback for receiving data (“next”) but I can also register optional callbacks to be notified of problems (“error”) or when there’s no more data (“complete”).

Operator: Documentation said this is the powerful part of RxJS, but didn’t really explain why or how we would leverage that power. This is also where marble diagrams were explained, something that bewildered me when Angular testing discussed marble testing. The overview of available operators is a disappointing list of just names. Each name is a link to their reference page without any additional context. I’d have to click the link and read each one. I would love a reference where each link has an 1-2 sentence summary, but no luck here.

Subject: These are Observable that multicasts to more than one Observer. Up until this point I hadn’t known a basic Observable only broadcast to a single Observer! This critical information should have been covered earlier.

Scheduler: No usage examples or scenarios were given so I have no idea when I should care about choosing a different RxJS scheduler. I see the “How to do X”, but not “Why you want to do X.”

I’m sure everything in official RxJS documentation is technically correct but the information lacks context. Or more precisely, I don’t think they were even trying to provide context for readers who are unaware. Perhaps there are resources to help RxJS beginners elsewhere on the internet?

Once my Angular development container could run tests in Chrome using headless mode, I could see actual test failures. Since “Tour of Heroes” tutorial did not touch test files at all, these failing tests were untouched boilerplate tests. For the most part they just test to see if a component instance could be created within the test harness, there were no further updates to test “Tour of Heroes” functionality. Components that couldn’t be created in a test harness obviously led to abysmal code coverage numbers.

=============================== Coverage summary ===============================
Statements   : 18.75% ( 15/80 )
Branches     : 0% ( 0/8 )
Functions    : 6.38% ( 3/47 )
Lines        : 16.21% ( 12/74 )
================================================================================

Since I am just getting started, there were a lot of (1) copy error message (2) search on that message (3) read hits on StackOverflow (4) repeat. Component creation failure mainly revolved around fixing up “imports” or declarations” sections to calling TestBed.configureTestingModule(). After I got component startup sorted out, code coverage numbers looked a lot better.

=============================== Coverage summary ===============================
Statements   : 61.25% ( 49/80 )
Branches     : 0% ( 0/8 )
Functions    : 53.19% ( 25/47 )
Lines        : 62.16% ( 46/74 )
================================================================================

But that was a lot of copy/pasting from StackOverflow with little understanding of what happened. And even though tests registered as passing, there were still error messages shown on console output. I need to learn more, so I started reading the “Testing” section of Angular Developer guides. It seems to assume I know Jasmine and Karma, which I don’t. I plan to skim the first pass for a partial understanding, then maybe dedicate some time to learning Jasmine/Karma, then come back again. Here are some notes from my first pass:

Valuable Live Examples

Just like the “Understanding Angular” section, pages in “Developer Guides” very frequently have a link to a project that we can load up and examine either by downloading code for our own machine or fire it up within our browser connected to a StackBlitz virtual machine. Having functional code is always great and mitigates many documentation issues. One code snippet in “Testing Services” documentation called a function I couldn’t find any information about, looking at the live code I figured out it was something strictly within the demo project. (async-observable-helpers.ts)

Scattered Older Content

I see occasional signs of outdated content. Some examples: (1) API TestBed.get() was deprecated from Angular 9 but still pops up here and there. (2) Occasional mentions of “Tour of Heroes” that doesn’t match the tutorial I just completed a second time. Either they were snippets from an older version of the tutorial, or the example was modified for illustration purposes. (3) Standard boilerplate code listed in “Basics of Testing Components” do not match what today’s tools generate.

Having illustrative code examples fall out of date reminded us to keep in mind that some of their associated information might be out of date as well.

Component Testing Scenarios

The longest page (by far) in this section is “Component Testing Scenarios.” I think it is the goldmine. A list of how we might want to test our Angular components and tools to go about them. It puts a lot of Angular testing tools (which have their own section) in context of problems they were created to solve. As a beginner I don’t quite understand why I might want to do these things, but here’s the reference if I want to do them.

Almost a quarter of this very long page is dedicated to “Component with async service”. (Which makes this one section longer than most other pages in “Angular Developer Guides – Testing”) RxJS is used by Angular a lot in the realm of asynchronous behavior, so I need to learn more about that. Not just to test, but to build Angular in general. I expect things will make sense after getting a better grasp of RxJS terminology like “marble testing“. I thought the best place to start would be RxJS official documentation. (I was wrong.)

Using the Angular Material component library gave me some great looking controls, but adding the library into my app increased its size by more than I had anticipated. It’s a good thing Angular Material is an optional component, so I don’t have to use it for space-constrained projects. Something else not core to Angular framework is page layout. I thought it might be part of Angular Material, but I found nothing there, either.

Looking around online for some kind of page layout component for Angular apps, I found something called “Angular Flex Layout” which, like Angular Material, is an optional component. It sounds like the component had always provided a bridge across the gap between the potential capabilities of CSS and the actual capabilities of CSS in shipping browsers. Several years ago, that gap was quite large! But now it appears the gap is small enough for Angular Flex Layout to ride off into the sunset.

I found more details on Angular team blog post “Modern CSS in Angular: Layouts“, which confirmed they intend for modern CSS (flexbox and grid got specific callouts) to handle most of what people formerly needed “Angular Flex layout” for. This blog post claimed to be the first in a series of helping people adopt modern standardized CSS for layout instead of using libraries like Angular Flex Layout, but I haven’t seen any additional installments posted. I’ll stay tuned hoping to learn more in the future.

For needs beyond modern CSS, that blog post pointed to layout-related features within Angular’s Component Development Kit (CDK). I read over some introductory pages and didn’t comprehend very much. I hope that after I become more familiar with CSS and Angular, I can articulate the gap CDK Layout fulfills.

And finally, that blog post also mentions using Tailwind CSS in Angular apps, but without further information. I know nothing about Tailwind and very little about Angular and CSS. At the moment I have no idea what tradeoffs are involved in using that library. I’ll stick that on my “To Do” list at the bottom. Right now I have a higher priority item on my list: get a handle on Angular unit testing.

I was interested in using Angular Material component library because I thought it would help me build web apps that look better than my usual efforts. My introductory experience with it was very promising and I think it’ll deliver on design aesthetics. The project was also an experiment to see other parts of Angular in action. On the topic of download size, the result was not as good.

One aspect of using Angular that sounded appealing was that it came with an already-configured build pipeline so I didn’t have to build my own. Starting from tools like TypeScript compiler, through to tools like Webpack. It is a multi-stage process to go from source code to a compact package delivered by our web server. It performs optimizations like “tree-shaking” for removing unused code, and “minification” which removed comments, whitespaces, everything nonessential. Ideally this meant the final package would have only what we absolutely need and no more. In practice, I’m not so sure.

After finishing the “Tour of Heroes” tutorial and playing with a bit of CSS, but before I converted over to using Angular Material, my application’s raw download size was a little over 309 kilobytes.

✔ Browser application bundle generation complete.
✔ Copying assets complete.
✔ Index html generation complete.

Initial Chunk Files           | Names         |  Raw Size | Estimated Transfer Size
main.e962da6362f99387.js      | main          | 274.74 kB |                71.19 kB
polyfills.716cc9a230a87077.js | polyfills     |  33.11 kB |                10.70 kB
runtime.6e50dac17b84e715.js   | runtime       | 922 bytes |               517 bytes
styles.19b697cb6d7ac4c1.css   | styles        | 477 bytes |               172 bytes

                              | Initial Total | 309.22 kB |                82.56 kB

After I installed Angular Material with “ng add @angular/material” but before I actually explicitly imported any components, the final bundle size grew by over 50% to 479 kilobytes:

✔ Browser application bundle generation complete.
✔ Copying assets complete.
✔ Index html generation complete.

Initial Chunk Files           | Names         |  Raw Size | Estimated Transfer Size
main.7c4c0522a82c6f83.js      | main          | 338.94 kB |                87.07 kB
styles.4aae9080591fb05a.css   | styles        | 106.13 kB |                 9.64 kB
polyfills.716cc9a230a87077.js | polyfills     |  33.11 kB |                10.70 kB
runtime.6e50dac17b84e715.js   | runtime       | 922 bytes |               517 bytes

                              | Initial Total | 479.08 kB |               107.92 kB

This was disappointing. As far as I know I haven’t actually used anything of Angular Material, yet I had already picked up 170 kilobytes of stuff that the automated optimization tools could not avoid. And even worse, this was completely opaque to me. I don’t know of any way to break down where those 170kB came from, nor what I could try to optimize them.

As I started actually importing and using components from Angular Material, my bundle size grew as expected. I had hoped maybe those 170 kilobytes were majority of core shared code and each additional module would add only minimal size, but this was definitely not the case. My freshman effort at Angular Material conversion added the following modules.

import { MatAutocompleteModule } from '@angular/material/autocomplete';
import { MatButtonModule } from '@angular/material/button';
import { MatIconModule } from '@angular/material/icon';
import { MatInputModule } from '@angular/material/input';
import { MatListModule } from '@angular/material/list';
import { MatToolbarModule } from '@angular/material/toolbar';

And by doing so, I picked up almost 300 additional kilobytes for a total of 776 kilobytes.

✔ Browser application bundle generation complete.
✔ Copying assets complete.
✔ Index html generation complete.

Initial Chunk Files           | Names         |  Raw Size | Estimated Transfer Size
main.dc2316f7fe149792.js      | main          | 636.43 kB |               134.91 kB
styles.7a21ac1018e81662.css   | styles        | 105.66 kB |                 9.52 kB
polyfills.716cc9a230a87077.js | polyfills     |  33.11 kB |                10.70 kB
runtime.6e50dac17b84e715.js   | runtime       | 922 bytes |               517 bytes

                              | Initial Total | 776.11 kB |               155.63 kB

Warning: bundle initial exceeded maximum budget. Budget 500.00 kB was not met by 276.11 kB with a total of 776.11 kB.

Final line of this output is a warning from Angular’s build-time bundle size budget watcher, which is half of a good feature. It’s great that it informed me I exceeded size budget, but I don’t understand what exactly contributed to that total and I certainly don’t know what I could do about it. Well, I guess there’s “Don’t use Angular Material” but I hope for something finer-grained than that.

Does this matter? It depends on the context. If I’m writing an app for my own use on my home network, a few hundred kilobytes are insignificant. If I’m writing something to run on my phone via mobile data, such data usage would be notable but not necessarily a deal breaker. If I’m creating a browser app from ESP32, there’s only 4MB of flash memory to serve such files and a few hundred kilobytes could sink the entire project.

It’s just like any other tool: there are right places to use it, and there are wrong places to use it. This applies to Angular itself, to Angular Material component library, and whatever I use for layout. Because for both good and ill, layout is not an intrinsic part of Angular framework.

I made some small layout and styling changes to Angular Framework’s “Tour of Heroes” tutorial app. It looked a little better to me, but those changes didn’t stick around for long. They were merely a HTML/CSS warmup exercise and quickly replaced by the next activity: converting the app to use Angular Material component library.

While I don’t necessarily agree with everything in Google’s Material Design, for better or worse Google’s reach meant most users would already be familiar with them. The option to utilize Angular Material component library was, in fact, the main motivation for me to learn Angular. Now that I’m finally at this point, I eagerly opened up their Getting Started page and got to work. The instructions were fine and putting the library to use was about as easy as I can reasonably ask for. There were two items of note:

Import

This was taught right up front on “Displaying a component” section of Getting Started page, but I didn’t grasp its significance at first. Each Angular Material component is packaged in a module that we have to import before use, making every component (and associated overhead) an opt-in decision. This is not illustrated by their live examples on Stackblitz, because those examples imported everything. I wasted time trying to sort out exactly what was important until I figured out that they tell you in the “API” section of each component’s documentation. Example: the first line of Material Button API page is:

import {MatButtonModule} from '@angular/material/button';

And Reload

After importing the module as per API documentation, I could use that component, but it didn’t look right. Most of the behaviors were there, but appearance-wise it didn’t look quite right. Style bits were missing here and there, the most visible aspect was that I didn’t see any theme colors. We’re supposed to be able to select from “Primary”, “Accent” or “Warn” colors but the control looked plain despite setting color to one of those options.

Hunting on answers from Stack Overflow found a lot of information about defining and using custom themes, which I don’t care about (yet). But buried among custom theming information was my answer: after importing a component, the development server launched by the “ng serve” command would only pick up partial functionality. There was nothing wrong with my code. To pick up everything, including theme colors, I had to stop the running instance of “ng serve” and launch it again.

Looks Great! But…

Getting this far meant I could fold several Angular Material controls into my “Tour of Heroes” app. Using Angular Material controls meant I could delete a lot of CSS associated with custom styling of the tutorial. Utilizing this component library in my own projects should mean less fussing with CSS for styling. This is a great benefit as I don’t consider myself any good at user interface design. But this ease has a tradeoff in larger download size.

Code for this project is publicly available on GitHub

Running through Angular framework’s “Tour of Heroes” tutorial a second time was good for me. I learned a lot of web development between my first and second runs, helping me understand and retain a lot more information this time around. I’m still short of what I’d call “proficient”, though. In the interest of getting more practice, I will continue my personal Angular learning plan. The main focus of “Tour of Heros” was Angular framework, so it had only minimal attention paid to styling. So my next step is to play with styling this tutorial app.

The main objective is to exercise “think in CSS” portions of my brain. As a computer user it’s not hard for me to think of web interfaces that I enjoyed and didn’t enjoy using. Now I want to develop an ability to articulate my experience in terms of how I can implement them in CSS. This will start out very slow and rough, with many visits to MDN documentation for reference. I expect to get faster at it with practice and practice starts small. This first round will make only minor changes to CSS and almost no changes to HTML at all.

It’s not necessary for results of this first round to be good in an objective sense, but it’s important for the layout to be mine. Pick out small things I didn’t like and verify I can fix it to my liking.

• Tutorial CSS used Cambria (a serif font) mixed in with majority of non-serif fonts. I felt those styles clashed for no good reason and that was the easiest place to start.
• I thought the diagnostics message section at the bottom took up too much space and wasn’t distinct enough from the rest of the app. My change packed the “Clear Messages” button on the same horizontal line as the header, removing a lot of whitespace around both. I also changed the diagnostic message text themselves to a monospaced font. This may sound hypocritical because I just removed some serif font usage because they clashed, but in this case a style clash is a feature and not a bug. I always mentally associate monospaced typefaces with technical data, and I wanted it to stand out.
• Dashboard component had a search box for hero names, and I thought that was not distinct enough from the rest of the dashboard. I gave it a subtly darker background to visually differentiate it from the rest of the dashboard, and I centered the component horizontally because Yahoo, Google, etc. all taught me to expect a search text box to be centered on screen.
• Similar to how I packed “Clear messages” into the same horizontal space as the message display area header, I packed “Dashboard” and “Heroes” navigation buttons into the same topmost horizontal space as the application header at the top of the screen.
• In the “Dashboard” view, we have a text box for search at the bottom. In the “Heroes” view, we have a text box for adding a new hero at the top. I didn’t like that ordering because I want to review existing data before I add a hero. I moved “add hero” control to the bottom, which also made it consistent with dashboard search.
• And finally, in the individual hero view, I again added a CSS flexbox to pack buttons together for a more compact layout.

I preferred how the resulting app looked, and I thought it was a good simple warmup round before I dip my toes into more serious UI styling.

Code for this project is publicly available on GitHub.

I’m glad I skimmed through “Understanding Angular” documentation section before going through “Tour of Heroes” tutorial for the second time. Combined with my improved understanding of web development, this time I actually understood everything covered in the tutorial. The best example are Angular directives, which were mysterious black boxes the first time around. I copied them straight from tutorial text without much comprehension of what they did. This time around, I mostly understood how they dictated Angular behavior. I also understood that some of what I see are shorthand versions and, if I get too lost, I can go look for their expanded-out full versions which are more explicit in their actions.

I Know Where Things Go Now

One memory I had of my first run of “Tour of Heroes” were a few steps where the instruction was to copy a snippet of code into a specific file. However, they didn’t say where in the file. The first time as a beginner, I didn’t even understand enough to know where a code snippet should fit. This time around, I never felt that way. When a code snippet is presented, I understood the context where it should be inserted. This was a very satisfying feeling! Once I completed “Tour of Heroes” for the second time (which also went much faster) I had a selection of topics to explore outside the scope of the tutorial.

Need to Revisit Angular Tests

One candidate is testing. At the moment I’m completely ignorant about automated testing of web apps. I know such tools exist, but so far, my web app projects were tested manually when I played around with what I wrote. As my project size grows (and I have ambitions of bigger projects) this approach would not scale well. Angular has provisions for testing frameworks, which we can kick off with “ng test”. Angular boilerplate includes a bare-bones test (filename ending with spec.ts) that went with the corresponding code (filename ending with just .ts.) Since the tutorial only changed code file without updating its corresponding test file, I ran “ng test” expecting to see test failures. But it appears I have some work to do before I even get that far, because I’m running Angular inside a VSCode dev container, and it doesn’t have Chrome installed.

node ➜ /workspaces/angular-tour-of-heroes (main) $ ng test
✔ Browser application bundle generation complete.
11 02 2023 09:44:34.255:WARN [karma]: No captured browser, open http://localhost:9876/
11 02 2023 09:44:34.268:INFO [karma-server]: Karma v6.4.1 server started at http://localhost:9876/
11 02 2023 09:44:34.268:INFO [launcher]: Launching browsers Chrome with concurrency unlimited
11 02 2023 09:44:34.272:INFO [launcher]: Starting browser Chrome
11 02 2023 09:44:34.273:ERROR [launcher]: No binary for Chrome browser on your platform.
  Please, set "CHROME_BIN" env variable.

I know it is possible to run Chrome in an automated test where it runs without any user interaction or even a visible interface. I’ll need to figure out this “headless mode” before I can run “ng test”.

After a few minutes of looking around online, it appears running headless Chrome inside a container requires more knowledge than I have at the moment. Instead of tackling another new thing, I decided to practice what I’ve already learned. I will resume my tentative learning plan, which calls for me to turn my Tour of Heroes into a CSS exercise.

My first time through Angular framework’s documentation section had focused on “Getting started” and “Tutorial” sections, just to get a toehold on things. Due to a firehose of information about this large framework, I didn’t retain very much. Now I’m taking a second pass through documentation, armed with more knowledge and experience to understand more of it. I drew up a tentative plan earlier, but I’ve already decided to deviate from that plan. After I read through the StackBlitz tutorial, but before I started hands-on with “Tour of Heroes” tutorial again, I decided to read the documentation section “Understanding Angular” whose overview page started with this:

To understand the capabilities of the Angular framework, you need to learn about the following:

• Components
• Templates
• Directives
• Dependency injection
  The topics in this section explain these features and concepts, and how you can use them.

I admire this goal, but the reality was I lacked prerequisite knowledge to understand all of it. This is fine! Every time I understand a little more. At a rough guess, I would say I understood and retained about 5% of this information after my first effort, and this second effort had roughly 30% retention.

Live Code Everywhere

The length and quality of documents in this section vary greatly, probably reflecting different authors contributing from their own perspectives. But at the end of the day, developers want to see code and we have them. Most (all?) of the topics included links to sample code in both live-running form (running on StackBlitz) as well as downloadable source code example. Some go much further, for example “component interaction” goes as far as including test code. And in several cases, sample code covered concepts that were not covered on written pages, so it’s always worth checking out that link.

Nonlinear Organization

Sometimes my confusion is not from missing prerequisite knowledge, but counterintuitive organization of information. For example: Under the binding section, Property binding is the next-to-last item on the list yet it is listed as prerequisite by the second (attribute binding) and third (class and style binding) documents. To make sense of everything I have to jump around this page.

Attributes vs. Properties

Several documents in the binding section emphasized that we bind to properties and not attributes. But they didn’t explain what that difference meant! Looking outside this site, I found this StackOverflow thread which included a gem of an explanation: “When writing HTML source code, you can define attributes on your HTML elements. Then, once the browser parses your code, a corresponding DOM node will be created. This node is an object, and therefore it has properties.“

Angular Directive Long Form

As an Angular beginner I can see Angular directives as a very powerful mechanism, but the syntax can be tough for me to decipher. Eventually I learned this was because we frequently see shorthands for using directives, and the structure is easier to comprehend when we see the “long form”. This snippet was shown as a *ngFor “long form”, and it was quite illuminating!

<div *ngFor="let product of products">
  <h3>
    <a [title]="product.name + ' details'">
      {{ product.name }}
    </a>
  </h3>
</div>

It was not as concise as the shorthand, but much easier for me to decipher what’s going on. Compare the above to another example of ngFor directive:

<ul>
  <ng-template ngFor let-hero [ngForOf]="heroes">
    <li>{{hero.name}}
  </ng-template>
</ul>

(Note that these are two different examples of ngFor and they do different things, because I copy/pasted them from different sections of Angular documentation. I’m only using them to compare syntax.)

Ready for Round 2

After reading through “Understanding Angular” I can’t say I totally understand Angular yet, but I have a much better understand of how it goes about its business. I expect some of this information to be reinforced as I go through their “Tour of Heroes” tutorial again, because I think I’ll recognize them the next time around and have a better idea of their usage context.

In the interest of improving the odds that I’ll actually learn something I can put to use, I’ve devised a plan for how I intend to learn and apply Angular application framework. My skills have evolved since the last time I ran through Angular tutorial, and it’s no surprise that Angular has evolved itself. Web technologies move fast! My previous effort worked with Angular 11, and as of about two weeks ago, we’re now up to Angular 15. I looked through the changes to see how much I understood and how much would actually affect the kind of projects I intend to build. It appears that I picked a good time to review Angular — v15 looks to be quite a consequential step forward.

From the “Angular v15 is now available” (2022/11/16) page:

• Standalone components: I got excited about this item because I didn’t understand Angular terminology. I thought “standalone” meant I could use Angular components piecemeal independent of the Angular framework, I was wrong. Reading more, I’ve learned some people felt Angular components are too dependent on a specific Angular mechanism “NgModule”. Architecturally that meant a NgModule was the smallest unit of reusability, and not Component as intended. This “standalone” feature makes it easier for an Angular Component to run without NgModule.
• NgOptimizedImage: Sounds like the Angular framework can now handle resizing image files. So large screen desktops don’t get blurry images and small mobile devices don’t waste bandwidth downloading high resolution images.
• Stack traces are more helpful: Sounds promising. Getting an informative stack trace has always been a problem with debugging asynchronous code.
• MDC-based components: Angular Material was why I started looking at Angular framework to begin with! At the time it was an Angular-focused set of web controls that are implemented differently from those intended for non-Angular web sites. (The non-Google affiliated Materialize-CSS project was something I’ve tried along similar veins.) Now it seems like the two worlds are converging, nice.

From the “Angular v14 is now available” (2022/6/2) page:

• Strictly typed forms: Reading the description, it’s the kind of thing that surprised in the “Wait, you meant it wasn’t like that already?” category. Angular uses TypeScript and leverages its compile time type checking to catch bugs. Given this fact I was surprised that forms (a major way to interact with user data) aren’t strictly typed. Perhaps there’s subtlety here I don’t understand but better type checking is almost always a good thing.

From the “Angular v13 is now available” (2021/11/3) page:

• End of IE11 support: This only impacts me because I have a bunch of old Windows Phones that I had intended to reuse in other projects via its integrated web browser, which is a mobile build of Internet Explorer. Angular 11 didn’t officially support IE but it was possible to build for IE with a few project settings. The results… mostly worked. As of Angular v13 that is no longer an option. If I still want to put those old Windows Phones to work via web apps, I’d have to do it with older versions of Angular or without Angular at all.

From the “Angular v12 is now available” (2021/5/12) page:

• Sass: I had forgotten about Sass until I read Angular v12 increased support for Sass. I learned about Sass quite some time ago, before my recent efforts to relearn CSS. I’ve forgotten much of Sass and how it addresses challenges of plain CSS. I’m going to refresh my knowledge of Sass before I proceed.