export declare class StringHelper {
    static isBlobUrl(val: string | null | undefined): boolean;
    static isEmail(val: string): boolean;
    static isNumeric(n: string): boolean;
    static isUrl(val: string): boolean;
    static isNullOrEmpty(str: string | null | undefined): boolean;
    static toKebabCase(str: string): string;
    static toSnakeCase(str: string): string;
    static truncate(str: string, length: number): string;
    static capitalizeFirstLetter(word: string): string;
    static toFileSizeString(sizeBytes: number): string;
}