1import { isUndefined } from "./Types";
 2
 3/**
 4 * Similar to Java's Optional. Better than using null, or undefined.
 5 */
 6
 7export class Optional<T> {
 8  private value: T | any = null;
 9
10  constructor(value?: T) {
11    this.value = value;
12  }
13
14  /**
15   * Create new Optional with the value. If the value is null will result in the same Optional as Optional.empty().
16   * @param value
17   */
18  static of<T>(value: T): Optional<T> {
19    return new Optional<T>(value);
20  }
21
22  /**
23   * Create new, empty optional.
24   */
25  static empty<T>(): Optional<T> {
26    return new Optional<T>();
27  }
28
29  /**
30   * Is the value in this Optional present, and non-null, and non-undefined?
31   */
32  isPresent(): boolean {
33    return !this.isEmpty();
34  }
35
36  /**
37   * Is the value in this Optional absent or null or undefined?
38   */
39  isEmpty(): boolean {
40    return this.value === null || isUndefined(this.value);
41  }
42
43  /**
44   * Get the value in this Optional. If the value is null or undefined, will return null or undefined.
45   */
46  get(): T {
47    return this.value;
48  }
49
50  /**
51   * If the value of this Optional is empty, null, or undefined, will return a given default value.
52   * @param defaultValue
53   */
54  getOrDefault(defaultValue: T): T {
55    return this.isEmpty() ? defaultValue : this.value;
56  }
57
58  /**
59   * Easy way to render what the value is, and indicate that this is an Optional.
60   */
61  public toString(): string {
62    return `Optional[${this.isEmpty() ? "null" : this.value}]`;
63  }
64}