Wednesday, June 16, 2021

Javascript: Self call re-call interval set

 So we have the requestAnimationFrame, you pass a function and it called after a very specific while (irrelevant to the following).

Now lets see the basic structure:

function loop() {

Ok now lets wrap the function and call it without calling it by name:

(function loop() {

Is there any way to remove the name of function and still pass it? There is a magical object called arguments which appears out of nothing every time a function is executed. And the member that we need is arguments.callee which is self reference to the function being executed. So we get rid of the name:

(function () {

And of course to maximize the coolness we put in a single line:

(function() { update(); requestAnimationFrame(arguments.callee) })()

Ok, this very cool, but is it worth it? Let's analyze what this code succeeds to do:

1. Confuses the next reader of the code.
2. Confuses also the 2nd reader.
3. Confuses also the 3rd reader.
N. Confuses also the N-th reader.

So you have to choose what is cooler: confusing no people or confusing up to infinite people? Comment below, like and subscribe.


Techniques: Build-time pre-package capture

 Usually when things/files are packaged from simple files to single monstrosity, you no longer have the ability to ls/dir to lookup what things/files exist.

An example is a Java jar, where to list for example all the packaged files you either cannot or you need to open a zip stream and figure out yourself.

Also in Java and other languages with limited introspection you cannot for example list all the classes that implement the interface X.


Create a script than generates all the information you want.

Put that script in the build/compile process.

Include the file in the project.

Write some code to parse the file.

Example of listing all the inheritance properties by finding all the extends keyword:

grep -hr extends | sed -E 's/.*class (\w+) extends (\w+) .*/\2 -> \1/'
Parent -> Child1
Parent -> Child2

No need to say again and again "This is not supported, I cannot do it", supported yourself, you are a damn programmer! 


Friday, June 11, 2021

Html: Input tag drop-down list

The classic way to have a drop-down list in html is the select tag.

However there are two main problems/inconvenient. The select tag will only allow to select one item and you cannot type for a not included option or just to filter the list options. Also sometimes just have all the input fields under the same tag name <input> is just niter.

An other way is the <datalist>, that for some reason I learned about it lately (sad).

The classic example:

<input list="hashes">
<datalist id="hashes">
  <option value="sha1">
  <option value="sha256">
  <option value="sha512">