/**
 * @hidden
 */
export const isPresent = (value: any): boolean => value !== null && value !== undefined;

/**
 * @hidden
 */
export const isBlank: Function = (value: any): boolean => value === null || value === undefined;

/**
 * @hidden
 */
export const isArray: Function = (value: any): boolean => Array.isArray(value);

/**
 * @hidden
 */
export const isFunction: Function = (value: any): boolean => typeof value === 'function';

/**
 * @hidden
 */
export const isString: Function = (value: any): boolean => typeof value === 'string';

/**
 * @hidden
 */
export const isTruthy: Function = (value: any): boolean => !!value;

/**
 * @hidden
 */
export const isNullOrEmptyString = (value: string): boolean => isBlank(value) || value.trim().length === 0;

/**
 * @hidden
 */
export const isNotNullOrEmptyString = (value: string): boolean => !isNullOrEmptyString(value);

/**
 * @hidden
 */
export const isNumeric: Function = (value: any): boolean => !isNaN(value - parseFloat(value));

/**
 * @hidden
 */
export const isDate: Function = (value: any): boolean => value && value.getTime;

/**
 * @hidden
 */
export type Pair<T, U> = [T, U];