Angular.js Updated 2025-07-16
React Updated 2025-07-16
React officially recommends that you use Next.js[ref], so just do it. It just sets up obvious missing functionality from raw React.
Its main design goal is to reduce DOM changes to improve rendering times.
And an important side effect of that is that it becomes easier to do stuff of the type:and then the new comment easily gets the callback attached to it.
- user creates a new comment that appears on screen without page reload
- comment has a delete button, which is JavaScript callback activated
But React can also be extremely hard to use. It can be very hard to know what you can and cannot do sometimes, then you have to stop and try to understand how react works things better:The biggest problem is that it is hard to automatically detect such errors, but perhaps this is the same for other frontend stuff. Though when doing server-side rendering, the setup should really tell you about such errors, so you don't just discover them in production later on.
- cannot update a component while rendering a different component warning in React
- Rendered more hooks than during the previous render.
- cannot use hooks from helpers:
Examples under: react.
- react/hello.html
- react/hello-func.html: Hello World with a React function component instead of classes. At page load console shows:and then after each click:
Mainso we understand thatonClick MainMaininsanely functions both as the constructor and as the render function in React function components. - react/hello-func-use-callback.html: same as react/hello-func.html but with useCallback. TODO no advantages in this case? When does it help?
- react/hello-without-jsx.html: Hello World in pure JavaScript, without JSX. Exactly equivalent to react/hello.html. Documented at: reactjs.org/docs/react-without-jsx.html Understanding this is fundamental to understanding React.
- By looking at the console, we see all
renderget called every time, even ifpropsdidn't change, but not the constructors.After page load the console contains:Main.constructor Main.render NotMain.constructor NotMain.render NotMain2.constructor NotMain2.renderNote how thepropsofNotMainonly change every other click, butrenderstill gets called every time.In order to makeReactnot re-render when there are not changes, you have to either:- define the
shouldComponentUpdatemethod of class components - wrap functional components in
React.memo
- define the
- react/prop-change-hook.html: same as react/prop-change.html, but using hooks. The notable difference is that functional components don't have a clear constructor/render separation, the function just gets called every time. Then React does some magic to ensure that
useStatereturns the current state, except for the first render where they return the initial value. - react/prop-change-hook-use-memo.html: TODO forgot if this example is useful, was tring to use
useMemo - react/prop-change-child.html: shows what child prop changes do not call render on parent,
Maindoes not show up on console when you click underNotMain - react/hook-from-function-fail.html: TODO got some errors that seemed linked to this on a larger program, but failed to minimize them here
- react/hook-different-number-of-times.html: this illustrates one of the cardinal points of using hooks: you must always call them the same number of times, otherwise it fails with:In the case of
React has detected a change in the order of Hooks called by Main. This will lead to bugs and errors if not fixed.
useState, we can kind of understand why this happens: React must use the order of calls to determine which state variable to return at each point in time. - react/hello-hook-use-effect.html: just checking when it gets called. Happens after every render
handleClick Main useEffect useEffect2 - TODO create a test
\a[react/img-broken.html]
How React works bibliography:
- www.netlify.com/blog/2019/03/11/deep-dive-how-do-react-hooks-really-work/ shows how
uesStateworks under the hood with crazy closures - medium.com/@gethylgeorge/how-virtual-dom-and-diffing-works-in-react-6fc805f9f84e
Vue.js Updated 2025-07-16
Linux Foundation Updated 2026-03-28
The fact that this foundation has a bunch of paid, closed, certification courses makes Ciro Santilli not respect them at all. They should be making open access content instead!
Linux insides Updated 2025-07-16
Documents the Linux kernel. Somewhat of a competitor to Linux Kernel Module Cheat, but more wordy and less automated.
Step debug the Linux kernel Updated 2025-07-16
Linux distribution buildable from source Updated 2025-07-16
As of 2020, no one knows how to build the major desktop distros fully from source into the ISO, and especially so in a reproducible build way. Everything is done in build servers somewhere with complicated layers of prebuilds. It's crap.
Package manager Updated 2025-07-16
Cross distro package manager Updated 2025-07-16
Gel electrophoresis separation of SNPs Updated 2025-07-16
- 1982 www.pnas.org/doi/pdf/10.1073/pnas.80.6.1579 DNA fragments differing by single base-pair substitutions are separated in denaturing gradient gels by Fischer and Lerman (1982). It is possible then.
Timelike-separated event Updated 2025-07-16
The opposite of spacelike-separated events.
Spacelike-separated event Updated 2025-07-16
Mathematically, we can decide if two events are timelike-separated or spacelike-separated by just looking at the sign of the spacetime interval between them.
On the light cone, these are events on the left/right part of the cone.
Different observers might not agree on the order of two spacelike-separated events.
Further discussion at Section "Light cone".
The opposite of those events are timelike-separated events.
Wave-particle duality Updated 2025-07-16
First people thought it was a particle, as per corpuscular theory of light, notably Newton supported the corpuscular theory of light.
But then evidence of the diffraction of light start to become unbearably strong, culminating in the Arago spot.
And finally it was understood from Maxwell's equations that light is a form of electromagnetic radiation, as its speed was perfectly predicted by the theory.
But then evidence of particle nature started to surface once again with the photoelectric effect. Physicists must have been driven mad by all these changes.
Light source Updated 2025-07-16
Optical fiber Updated 2025-07-16
Fiber optics fundamentals by Shaoul Ezekiel
. Source. 2008 at MIT. Theory and demonstration.- youtu.be/0DCrIAxEv_Y?t=560:Terefore, the 1.5 micrometer window truly is the minimum.
- on smaller wavelengths, loss is due to Rayleigh scattering
- on longer wavelengths, loss is due to material absorption
Photometer Updated 2025-07-16
Spectroscopy Updated 2025-07-16
Speed of light Updated 2025-07-16
Electromagnetic spectrum Updated 2025-07-16
libgit2/rugged Updated 2025-07-16
There are unlisted articles, also show them or only show them.