HTML

Theme-based stylesheets

<link rel="stylesheet" href="light.css" media="(prefers-color-scheme: light)">
<link rel="stylesheet" href="dark.css" media="(prefers-color-scheme: dark)">

This is not supported by IE and other lesser known browsers.

JavaScript

Asynchronous functions in loops

const start = 0;
const end = 5;

for (i = start; i < end; i++) {
    setTimeout(() => {
        console.log(i); // -> 5, 5, 5, 5, 5
    });
};

function forSync(i) {
    setTimeout(() => {
        console.log(i); // -> 0, 1, 2, 3, 4
        if (i + 1 < end) forSync(i + 1);
    });
};
forSync(start);

This allows for asynchronous functions by placing the callback within that function.

Export promise with arguments

const module = require("./module");
module("Hello!").then(console.log); // -> Hello!

module.exports = (input) => {
    return new Promise((resolve, reject) => resolve(input));
};

exports won't work, only module.exports will!

Get DOM element from jQuery element

$("#foo")[0];
$("#foo").get(0);

Use either, see the jQuery FAQ.

insertAdjacentHTML() positions

<!-- beforebegin -->
<parent>
    <!-- afterbegin -->
    <child></child>
    <!-- beforeend -->
</parent>
<!-- afterend -->

Copied from the MDN documentation.

Swap out variable values

var a = 1;
var b = 2;

[a, b] = [b, a];

console.log(a); // -> 2
console.log(b); // -> 1

You can also specify more (or less) than two variables.

Write to clipboard

navigator.clipboard.writeText("Text").then(function() {
    // Success!
}, function() {
    // Error!
});

This is not supported in IE, and Firefox hides it behind a flag.

PHP

Temporarily disable Composer cache

COMPOSER_CACHE_DIR=/dev/null composer

See the Composer documentation for details.

Use PHP variables in variable names

$foo = "bar";
$$foo = "baz";
echo $bar; // -> baz

Here, $$foo resolves to $bar!

Other

Connect via ZOC from WinSCP

WinSCP → Options → Preferences → Applications → PuTTY/Terminal client path:

"zoc.exe" /CONNECT:!U:!P@!@:!# "/RUN:%USERPROFILE%\Documents\ZOC8 Files\REXX\cd.zrx" "/RUNARG:!/"

%USERPROFILE%\Documents\ZOC8 Files\REXX\cd.zrx:

CALL ZocSend "cd '"ARG(1)"'^M"

Create new PostgreSQL user and database

CREATE DATABASE database;
CREATE USER user WITH ENCRYPTED PASSWORD password;
GRANT ALL PRIVILEGES ON DATABASE database TO user;

Fix error 0x80073D05 when installing Ubuntu on Windows

Remove-Item -Recurse $env:LOCALAPPDATA/Packages/CanonicalGroupLimited.UbuntuonWindows_79rhkp1fndgsc

Re-use blocks in Caddyfile

(foo) {
    log
}

example.com {
    import foo
}

See the Caddy documentation for details.