typescript source code of fileutils

import { normalizePath } from 'obsidian';
import path from 'path';

export function isValidUrl(url: string): boolean {
    try {
        new URL(url);
    } catch (e) {
        return false;
    }
    return true;
}

export function getBaseUrl(url?: string, prefix?: string): string {
    const dir = '/';
    const urlAsArray = url.split(dir);
    const doubleSlashIndex = url.indexOf('://');
    if (doubleSlashIndex !== -1 && doubleSlashIndex === url.indexOf(dir) - 1) {
        urlAsArray.length = 3;
        let url = urlAsArray.join(dir);
        if (prefix !== undefined) url = url.replace(/http:\/\/|https:\/\//, prefix);
        return url;
    } else {
        const pointIndex = url.indexOf('.');
        if (pointIndex !== -1 && pointIndex !== 0) {
            return (prefix !== undefined ? prefix : 'https://') + urlAsArray[0];
        }
    }
}

export function normalizeFilename(fileName: string): string {
    const illegalSymbols = [':', '#', '/', '\\', '|', '?', '*', '<', '>', '"'];
    if (illegalSymbols.some((el) => fileName.contains(el))) {
        illegalSymbols.forEach((ilSymbol) => {
            fileName = fileName.replace(ilSymbol, '');
        });

        return fileName;
    } else {
        return fileName;
    }
}

export function pathJoin(dir: string, subpath: string): string {
    const result = path.join(dir, subpath);
    // it seems that obsidian do not understand paths with backslashes in Windows, so turn them into forward slashes
    return normalizePath(result.replace(/\\/g, '/'));
}