/**
 * returns a promise that will resolve in the specified number of
 * milliseconds
 */
export declare function sleep(milliseconds?: number): Promise<unknown>;
/**
 * generates a random string guaranteed to start with an alpha
 * character, which makes it suitable for HTML `id` attribute
 */
export declare function randomid(length?: number): string;
/**
 * useful for checking for empty strings, though in modern javascript
 * optional chaining may be easier: if (!str?.trim().length) ...
 */
export declare function isBlank(str: string | undefined | null): str is '' | undefined | null;
/**
 * useful for checking for empty strings, though in modern javascript
 * optional chaining may be easier: if (str?.trim().length) ...
 */
export declare function isNotBlank<T extends string | undefined | null>(str: T): str is Exclude<T, undefined | null>;
/**
 * useful for chaining Array.filter(isTruthy).map when using typescript; the map
 * variable will no longer be marked as optional
 *
 * also see: isNotNull
 */
export declare function isTruthy<T>(str: T): str is Exclude<T, undefined | null>;
/**
 * undefined and null both treated as null
 */
export declare function isNull(obj: any): obj is undefined | null;
/**
 * undefined and null both treated as null
 */
export declare function isNotNull<T>(obj: T): obj is Exclude<T, undefined | null>;
/**
 * only checks for valid syntax
 */
export declare function isEmail<T extends string | undefined | null>(email: T): email is Exclude<T, undefined | null>;
interface Stringable {
    toString: (...args: any) => string;
}
/**
 * Convert something to a string but convert null|undefined to undefined instead of creating
 * 'undefined' and 'null' strings
 */
export declare function optionalString(str: number | string | boolean | Stringable): string;
export declare function optionalString(str: undefined | null): undefined;
export declare function optionalString(str: any): string | undefined;
/**
 * Print a variable if a condition is met
 *
 * Optionally provide a boolean as the first parameter to control whether to print anything.
 * For example, `printIf(mystate.showcontent, mystate.content)` will print the contents of
 * mystate.content only if mystate.showcontent is truthy.
 *
 * Always outputs an empty string instead of 'undefined' or 'null', so you do not have to
 * explicitly check mystate.content against null.
 *
 * Generally shorter/easier than (mystate.showcontent && mystate.content != null ? mystate.content : '')
 *
 * @note This isn't intended for use with string interpolation passed to `str` as the interpolation will evaluate
 * as a parameter to the function before entering this function and testing the conditional.
 */
export declare function printIf(condition: any, str: number | string | boolean | Stringable | undefined | null): string;
export declare function printIf(str: number | string | boolean | Stringable | undefined | null): string;
export declare function roundTo(num: number, digits?: number): number;
export declare function bytesToHuman(bytes: number): string;
export {};