/**
 * a collection of string utility functions
 */
/**
 * converts the first character of the given string to uppercase
 * @param str - the string to be capitalized
 * @returns the capitalized string
 */
export declare function capitalize(str: string): string;
/**
 * returns true if the given string contains a numeric integer or float value
 * @param str - the string to be tested
 * @returns true if string contains only digits
 */
export declare function isNumeric(str: string): boolean;
/**
 * returns true if the given string contains a true or false
 * @param str - the string to be tested
 * @returns true if the string is either true or false
 */
export declare function isBoolean(str: string): boolean;
/**
 * convert a string to the corresponding hexadecimal value
 * @param str - the string to be converted
 * @returns the converted hexadecimal value
 */
export declare function toHex(str: string): string;
/**
 * returns true if the given string is a data url in the `data:[<mediatype>][;base64],<data>` format.
 * (this will not test the validity of the Data or Base64 encoding)
 * @param str - the string (url) to be tested
 * @returns true if the string is a data url
 */
export declare function isDataUrl(str: string): boolean;
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