Validator for file extensions

gistfile1.txt

/**
 * Validator of file extensions
 */
export class ExtensionValidator {
    private readonly detector = new ExtensionDetector();

    constructor() {
    }

    /**
     * E.g. 'txt' from 'example.txt'
     * @param filename
     * @param extension extension text without a dot
     * @param case_sensitive default:false
     */
    hasExtension(filename: string, extension: string, case_sensitive?: boolean): boolean {
        const fileExtension = this.detector.getExtension(filename).substring(1); // removing the dot

        if (case_sensitive) {
            return fileExtension === extension
        } else {
            return filename.toLowerCase() === extension.toLowerCase();
        }

    }

    /**
     * @return void on match.  e.g. 'txt' from 'example.txt'
     * @throws Invalid extension
     */
    check(filename: string, extension: string, case_sensitive?: boolean): void {
        const fileExtension = this.detector.getExtension(filename);
        if (case_sensitive) {
            if (fileExtension === extension) return;
        } else {
            if (filename.toLowerCase() === extension.toLowerCase()) return;
        }
        throw new Error("Invalid extension");
    }

}