Two days before release — and guess what? Suddenly, all popovers with information about meeting rooms in our app broke and stopped displaying. We hadn’t even changed anything related to this functionality — how could this happen?
Situation
It turned out that the popovers were broken in all browsers except Chrome. And after the latest Chrome update, they stopped working there too.
What happened?
Four years ago, someone decided it was fine to hide a <g> element using display: none, but still call node.getBoundingClientRect() on its child elements to calculate the popover’s position.
It worked… until it didn’t. Now, all modern browsers correctly return zero for the coordinates and size of any child inside a display: none element.
To be honest, I didn’t want to refactor much, so I replaced display: none with opacity: 0. In this case, the element is still invisible to the user but remains in the document flow and keeps its size.
I hadn’t parsed a JWT token on the client before, but this week our backender said that he
didn’t have time to create a new endpoint like /user, and that I should extract user information
from the JWT token in a cookie.
My first thought was: is this okay? On all projects that I’ve seen backend gave me endpoint like
/user, /me, /current — and these endpoints were created for a reason, weren’t they?
Yes, there are reasons:
you cannot store sensitive, confidential information in JWT payload
you should be mindful of the size of the JWT (it is transmitted with cookies in every request)
For example, it is not a good idea to store in JWT permissions for user and rely on it in your
UI. Because someone can modify the token, and your application could be at risk.
However, this means you can use a JWT to store some basic user information. In my current
situation, I only need name, email and photo of the authorized user, so I started parsing JWT for
this data and backend developer took another task.
What do you need for parsing JWT on client?
JWTs are Base64 encoded and contain of three parts: header, payload, and signature. You can
write your own decoding function or use one of the ready-made solutions. I checked what is there on
the internet for handling JWT tokens on the client-side:
jsonwebtoken — very popular library for Node.js.
It is used for generating and verifying JWTs on the server-side, can be used on the client side.
It’s a good library, but overkill for my case.
jose — another library for implementing JWT, it provides
functionality for signing and verifying tokens and set of utility functions. Again: good, but
overkill for my case.
jwt-decode — lightweight library only for decoding
tokens. Single-purpose, easy to use, zero dependencies — that’s the winner for today.
I’ve been using Cursor for 3 weeks, and I’m really impressed. Of course, it is not ideal and it
doesn’t replace a human developer (for now), but it can help in a lot of ways.
My favorite uses for it are writing tests with instructions, creating TS types, and
drawing diagrams. Let’s look closer at each case.
Writing tests
Not all developers love to write unit and integration tests. I personally lose my inspiration
when I need to create a lot of mocks, do some routine tasks for preparing the test environment and
try to make everything work with components or other libraries.
And that’s the place where AI shines! Of course not without a helping hand, but…
How I improved results of generation
created mdx files with instructions for writing tests with examples (separate files
for unit and integration tests)
described the flow: AI ought to write tests, after that run them and check results. If there are
failed tests, AI fixes them
run command write tests for ... and add relevant instructions to the context
Of course, there is still a lot of work with reviewing, but with mocks and setting up
environments it helps a lot.
Generating types
When you get a new endpoint and add it to your application, you need to describe types. In all our
projects we use TypeScript, and before starting to use AI I created types manually (there is
Swagger only on some of the projects). But now… I just need to give the API response to AI and
describe what it is and some constraints — and after a few minutes I have generated types. There
is room for improvement, but it speeds me up a lot.
Diagrams
I love diagrams, and I believe that it is easier to understand processes and technical details
from diagrams and schemes, not from plain text. And I explored a whole new world for me with
this prompt: @project explain how is ___ implemented and draw a scheme of how ____ works.
I can read and have a mermaid diagram (I just copy and paste in an online mermaid editor) in front of
my eyes — it has simplified a lot.
I’ve been refactoring our codebase, and it seems like my colleagues from the past were very fond
of the
<b> tag. They’ve used it a lot. I am not a big fan, especially of code like this:
.componentb {
font-weight: normal;
}
But maybe there is some reason why these guys applied it everywhere? Let’s research a little!
<b> now
I knew that <b> was for Bold. As I found out, now this is not the case. The HTML5 specification says:
The b element represents a span of text to which attention is being drawn for utilitarian purposes without conveying any extra importance and with no implication of an alternate voice or mood, such as key words in a document abstract, product names in a review, actionable words in interactive text-driven software, or an article lede.
And adds:
The b element should be used as a last resort when no other element is more appropriate.
For me, it is a really confusing tag now: there are some ideas about appearance (and browsers
support it), but <b> is not about appearance. Issues with this tag are presented in the W3C
article “Using <b> and <i> elements”.
I plan to get rid of <b> in most places of my code and try to use h1-h6, em, strong
or mark — a pretty wide choice!
Я уже сталкивалась с этим и уже удивлялась этому поведению, но позабыла — и поэтому сегодня потратила
на отладку пару часов: подозревала в коварстве библиотеку компонентов, которую использую,
искала проблемы в композиции и отлаживала изменения контекста.
Итак, что было? В нашем App.tsx:
<Routerhistory={history}>
<UuiContext.Providervalue={services}>
<Header />
<Routes />
<Footer />
</UuiContext.Provider>
</Router>
В Header.tsx — навигация:
// компонент из библиотеки, у него есть подсветка активного пункта меню.
// заглядывает в uuiContext от UuiContext.Provider и проверят, активная ли линка через history
И вроде всё (ну, почти всё) работает: по кликам в MainMenu урл обновляется, контент перерисовывается.
Вот только нет выделения активного элемента в MainMenu.
Начинаю разбираться, почему — ставлю точку остановы в фукнцию в MainMenu.tsx, где определяется, активная ли
линка. И тут начинается интересное: при переходе по кнопкам и обновлении урла функция не вызывается.
Добавляю console.log(‘render’) в Header.tsx. Что ж, он не пере-рендеривается, так что логично,
что ничего не происходит. Но ведь мы же вроде обновляем историю, а в uuiContext.uuiRouter.history —
как раз всё обновляется… Почему же дочерние элементы UuiContext.Provider не обновляются?
Тут я пошла неверным путём: попыталась отладиться в контекстах, потому что заподозрила, что у меня
где-то создается несколько инстансов и происходит путаница. Ничего не нашла, естественно.
После блуждания по контекстам, в мою голову пришла мысль: содержимое страницы обновляется за счет
изменения актуального Route — поэтому часть в Routes перерендеривается нормально. Что, если Header
положить внутрь каждой страницы, соответствующей роуту?
Это помогло, однако в таком случае Header каждый раз при изменении роута unmount и mount. Выглядит
некрасиво и излишне.
И вот тут наконец хороший вопрос пришел в голову: как React Router определяет, что надо что-то
пере-рендерить? И вот что я выяснила:
мы обновляем history
history object имеет постоянную ссылку
useHistory поэтому все время будет возвращать один и тот же объект, поэтому useEffect c
history.location не отработает при изменении location
зато вот useLocation и useParams следят за изменениями локации, поэтому как только мы их используем —
наш компонент начинает пере-рендериваться при изменениях
Самое противное, что у меня уже была подобная проблема, но вспомнила о ней и об этом моменте я только тогда,
когда “заново” нашла решение. Записываю сюда, чтобы больше не забывать 🤪