To evaluate how `URL(url).hostname` in JS handles discarded characters and character conversions in domain names.

urlhostname_test.js

// by @irsdl
// This script identifies anomalies in how JS parses the URL using `URL(url).hostname`:
// 1- Characters that are ignored when present in the domain name.
// 2- Characters that can replace ASCII characters in domain names and still be parsed correctly. In here we want letter S in `soroush.me`
// You can try running this script in your browser's dev console or at https://www.jdoodle.com/execute-nodejs-online/
// I am sure this must have been looked at before but I cannot find a reference

for (let i = 0; i <= 0xFFFF; i++) {
    const unicodeChar = String.fromCharCode(i);
    const urlString = `http://sorous${unicodeChar}h.me/blog/`;
    try {
        const { hostname } = new URL(urlString);
        if (hostname === 'soroush.me') {
            console.log(`Ignored Unicode: ${unicodeChar.charCodeAt(0).toString(16).padStart(4, '0').toUpperCase()}`);
        }
    } catch (error) {
        
    }
}

for (let i = 0; i <= 0xFFFF; i++) {
    const unicodeChar = String.fromCharCode(i);
    const urlString = `http://${unicodeChar}oroush.me/blog/`;
    try {
        const { hostname } = new URL(urlString);
        if (hostname === 'soroush.me') {
            console.log(`Unicode for letter S: ${unicodeChar.charCodeAt(0).toString(16).padStart(4, '0').toUpperCase()}`);
        }
    } catch (error) {
        
    }
}

/*
Expected results:

Ignored Unicode: 0009
Ignored Unicode: 000A
Ignored Unicode: 000D
Ignored Unicode: 00AD
Ignored Unicode: 034F
Ignored Unicode: 180B
Ignored Unicode: 180C
Ignored Unicode: 180D
Ignored Unicode: 180F
Ignored Unicode: 200B
Ignored Unicode: 2060
Ignored Unicode: 2064
Ignored Unicode: FE00
Ignored Unicode: FE01
Ignored Unicode: FE02
Ignored Unicode: FE03
Ignored Unicode: FE04
Ignored Unicode: FE05
Ignored Unicode: FE06
Ignored Unicode: FE07
Ignored Unicode: FE08
Ignored Unicode: FE09
Ignored Unicode: FE0A
Ignored Unicode: FE0B
Ignored Unicode: FE0C
Ignored Unicode: FE0D
Ignored Unicode: FE0E
Ignored Unicode: FE0F
Ignored Unicode: FEFF
Unicode for letter S: 0053
Unicode for letter S: 0073
Unicode for letter S: 017F
Unicode for letter S: 02E2
Unicode for letter S: 209B
Unicode for letter S: 24C8
Unicode for letter S: 24E2
Unicode for letter S: FF33
Unicode for letter S: FF53

*/

Better output:

const ignoredUnicodes = [];
const sSubstituteUnicodes = [];

for (let i = 0; i <= 0xFFFF; i++) {
    const unicodeChar = String.fromCharCode(i);
    const urlString = `http://sorous${unicodeChar}h.me/blog/`;
    try {
        const { hostname } = new URL(urlString);
        if (hostname === 'soroush.me') {
            ignoredUnicodes.push(`${unicodeChar.charCodeAt(0).toString(16).padStart(4, '0').toUpperCase()}`);
        }
    } catch (error) {
        // Error handling can be added if needed
    }
}

for (let i = 0; i <= 0xFFFF; i++) {
    const unicodeChar = String.fromCharCode(i);
    const urlString = `http://${unicodeChar}oroush.me/blog/`;
    try {
        const { hostname } = new URL(urlString);
        if (hostname === 'soroush.me') {
            sSubstituteUnicodes.push(`${unicodeChar.charCodeAt(0).toString(16).padStart(4, '0').toUpperCase()}`);
        }
    } catch (error) {
        // Error handling can be added if needed
    }
}

// Output the results
console.log(`Ignored Unicode: ${ignoredUnicodes.join(', ')}\n\nUnicode for letter S: ${sSubstituteUnicodes.join(', ')}`);

Result:

Ignored Unicode: 0009, 000A, 000D, 00AD, 034F, 180B, 180C, 180D, 180F, 200B, 2060, 2064, FE00, FE01, FE02, FE03, FE04, FE05, FE06, FE07, FE08, FE09, FE0A, FE0B, FE0C, FE0D, FE0E, FE0F, FEFF

Unicode for letter S: 0053, 0073, 017F, 02E2, 209B, 24C8, 24E2, FF33, FF53