feat: add repeat() (#126)

README.md

@@ -29,6 +29,11 @@ assertron.throws(() => Promise.reject(new Error('foo')))
 assertron.pathEqual('dir/sub-dir/file.txt', 'dir\\sub-dir\\file.txt')
 ```
 
+### assertron.repeat(fn, times)
+
+Repeat the specified function n times and return the last result.
+If the result is a promise, it will run the function sequentially.
+
 ### assertron.satisfies(actual, expected)
 
 `assertron.satisfies()` checks if `actual` meets the requirements specified by `expected`.

src/assertron/assertron.ts

@@ -2,12 +2,12 @@ import AssertionError from 'assertion-error';
 import { falsy } from './falsy';
 import { pathEqual } from './pathEqual';
 import { rejects } from './rejects';
+import { repeat } from './repeat';
 import { resolves } from './resolves';
 import { satisfies } from './satisfies';
 import { throws } from './throws';
 import { truthy } from './truthy';
 
-
 export const assertron = {
   false(value: any) {
     if (value !== false)
@@ -19,6 +19,7 @@ export const assertron = {
   falsy,
   pathEqual,
   rejects,
+  repeat,
   resolves,
   satisfies,
   throws,

src/assertron/repeat.spec.ts

@@ -0,0 +1,23 @@
+import a from '..'
+
+test('repeat function n times', () => {
+  let count = 0
+  a.repeat(() => ++count, 10)
+
+  expect(count).toBe(10)
+})
+
+test('repeat async function n times sequentially', async () => {
+  let count = 0
+  let actual = ''
+  let aa = await a.repeat(() => new Promise<string>(a => {
+    setTimeout(() => {
+      ++count
+      actual += String(count)
+      a(actual)
+    }, Math.random() * 10)
+  }), 10)
+
+  expect(actual).toBe('12345678910')
+  expect(actual).toBe(aa)
+})

src/assertron/repeat.ts

@@ -0,0 +1,20 @@
+import isPromise from 'is-promise';
+
+/**
+ * Repeat the specified function n times and return the last result.
+ * If the result is a promise, it will run the function sequentially.
+ */
+export function repeat<R>(fn: () => R | (() => Promise<R>), times: number): ReturnType<typeof fn> extends Promise<R> ? Promise<R> : R {
+  const result = fn()
+  if (isPromise(result)) {
+    if (times <= 1) return result as any
+    return result.then(() => repeat(fn, times - 1)) as any
+  }
+  else {
+    let result
+    for (let i = 1; i < times; i++) {
+      result = fn()
+    }
+    return result
+  }
+}