export declare function now(): number;
/**
 * @classdesc
 * Utilities methods used internally. It is static and should not be initiated.
 * @class
 * @static
 * @category core
 * @name Util
 */
/**
 * Merges the properties of sources into destination object.
 * @param dest
 * @param source
 * @return
 * @module Util
 */
export declare function extend<T extends {}, U>(dest: T, source: U): T & U;
export declare function extend<T extends {}, U, V>(dest: T, source1: U, source2: V): T & U & V;
export declare function extend<T extends {}, U, V, W>(dest: T, source1: U, source2: V, source3: W): T & U & V & W;
export declare function extend<T extends {}, U, V, W, X>(dest: T, source1: U, source2: V, source3: W, source4: X): T & U & V & W & X;
export declare function extend(dest: object, ...args: Array<any>): any;
/**
 * Whether the object is null or undefined.
 * @param  obj - object
 * @return
 * @memberOf Util
 */
export declare function isNil(obj: Object): obj is null;
/**
 * Whether val is a number and not a NaN.
 * @param  val - val
 * @return
 * @memberOf Util
 */
export declare function isNumber(val: Object): val is number;
/**
 * Whether a number is an integer
 * @param  n
 * @return
 * @memberOf Util
 */
export declare function isInteger(n: number): boolean;
/**
 * Whether the obj is a javascript object.
 * @param obj  - object
 * @return
 * @memberOf Util
 */
export declare function isObject(obj: Object): obj is object;
/**
 * Check whether the object is a string
 * @param obj
 * @return
 * @memberOf Util
 */
export declare function isString(obj: Object): obj is string;
/**
 * Check whether the object is a function
 * @param {Object} obj
 * @return {Boolean}
 * @memberOf Util
 */
export declare function isFunction(obj: Object): obj is Function;
/**
 * Check whether the object owns the property.
 * @param obj - object
 * @param key - property
 * @return
 * @memberOf Util
 */
export declare function hasOwn(obj: Object, key: string): boolean;
/**
 * Join an array, standard or a typed one.
 * @param  arr       array to join
 * @param  seperator  seperator
 * @return  result string
 * @private
 * @memberOf Util
 */
export declare function join(arr: Object[], seperator: string): string;
/**
 * Determine if an object has any properties.
 * @param object The object to check.
 * @returns The object is empty
 * @memberOf Util
 */
export declare function isEmpty(object: Object): boolean;
export declare function toRadian(d: number): number;
export declare function toDegree(r: number): number;
export declare function warnOnce(message: any): void;
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