/**
 * Returns true if all characters in a **string** are letters and there is at least one character.
 */
export declare function isAlpha(string: string): boolean;
/**
 * Returns true if all characters in a **string** are numeric digits and there is at least one character.
 */
export declare function isDigit(string: string): boolean;
/**
 * Returns true if all letter characters in a **string** are lowercase and there is at least one character.
 */
export declare function isLower(string: string): boolean;
/**
 * Returns true if all letter characters in a **string** are uppercase and there is at least one character.
 */
export declare function isUpper(string: string): boolean;
/**
 * Returns true if a **string** is empty or all characters in a **string** are whitespace.
 */
export declare function isBlank(string: string): boolean;
/**
 * Converts a **string** to lowercase.
 */
export declare function lower(string: string): string;
/**
 * Evenly pads both sides of a **string** with spaces such that the resulting string has a specified **length**.
 * Returns the original string if it has a length greater than or equal to the specified **length**.
 */
export declare function pad(string: string, length: number): string;
/**
 * Evenly pads both sides of a **string** with characters from **padding** such that the resulting string has a
 * specified **length**. Returns the original string if it has a length greater than or equal to the specified **length**.
 */
export declare function pad(string: string, length: number, padding: string): string;
/**
 * Pads the start of a **string** with spaces such that the resulting string has a specified **length**. Returns the
 * original string if it has a length greater than or equal to the specified **length**.
 */
export declare function padStart(string: string, length: number): string;
/**
 * Pads the start of a **string** with characters from **padding** such that the resulting string has a specified
 * **length**. Returns the original string if it has a length greater than or equal to the specified **length**.
 */
export declare function padStart(string: string, length: number, padding: string): string;
/**
 * Pads the end of a **string** with spaces such that the resulting string has a specified **length**. Returns the
 * original string if it has a length greater than or equal to the specified **length**.
 */
export declare function padEnd(string: string, length: number): string;
/**
 * Pads the start of a **string** with characters from **padding** such that the resulting string has a specified
 * **length**. Returns the original string if it has a length greater than or equal to the specified **length**.
 */
export declare function padEnd(string: string, length: number, padding: string): string;
/**
 * Converts a **string** to uppercase.
 */
export declare function upper(string: string): string;