feat: add isPromiseLike (#474)

- closed #473

Author: SevereCloud

src/index.ts

@@ -110,6 +110,7 @@ export {
   isFormData,
   isString,
   isNumber,
+  isPromiseLike,
 } from './type_checkers';
 
 export type { Dictionary, AnyFunction, SupportEvent, TimeoutHandle, Writeable } from './types';

src/type_checkers.test.ts

@@ -0,0 +1,18 @@
+/* eslint-disable @typescript-eslint/no-empty-function */
+import { describe, expect, test } from '@jest/globals';
+import { isPromiseLike } from './type_checkers';
+
+describe(isPromiseLike, () => {
+  const promise = { then: function () {} };
+
+  const fn = () => {};
+  fn.then = () => {};
+
+  test.each<any>([promise, fn])('isPromiseLike(%s) is true', (a) => {
+    expect(isPromiseLike(a)).toBeTruthy();
+  });
+
+  test.each<any>([{}, () => {}, { then: true }, [], [true]])('isPromiseLike(%s) is false', (a) => {
+    expect(isPromiseLike(a)).toBeFalsy();
+  });
+});

src/type_checkers.ts

@@ -29,3 +29,7 @@ export function isString(object: any): object is string {
 export function isNumber(object: any): object is number {
   return typeof object === 'number';
 }
+
+export function isPromiseLike<T = any>(object: any): object is PromiseLike<T> {
+  return (isObject(object) || isFunction(object)) && isFunction(object.then);
+}