@reusable-ui/icon/src/utilities.ts

An icon set component for React app.

// utilities:
/**
 * Merges two specified url to final url.
 * @param base The relative or absolute base url.
 * @param target The relative or absolute target url.
 * @returns A final url.  
 * If `target` is an absolute url, the `base` discarded.  
 * Otherwise, the combination of `base` url followed by `target` url.
 */
export const concatUrl = (base: string, target: string): string => {
    const dummyUrl  = new URL('http://dummy');
    if (!base.endsWith('/') || !base.endsWith('\\')) base += '/';
    const baseUrl   = new URL(base, dummyUrl);
    const targetUrl = new URL(target, baseUrl);
    
    const result = targetUrl.href;
    if (result.startsWith(dummyUrl.origin)) return result.slice(dummyUrl.origin.length);
    return result;
};

/**
 * Gets a file format based on the extension of the specified `fileName`.
 * @param fileName The name of the file to retrieve.
 * @returns  
 * A `string` represents a file format.  
 * -or-  
 * `null` if the format file is unknown.
 */
export const formatOf = (fileName: string): string|null => {
    if (!fileName) return null;
    
    
    
    const lastDotIndex = fileName.lastIndexOf('.');
    if (lastDotIndex < 0) return null; // extension is not found
    const extension = fileName.slice(lastDotIndex + 1).toLowerCase();
    switch (extension) {
        case 'ttf': return 'format("truetype")';
        default   : return  `format("${extension}")`;
    } // case
};