Travis build: 1057

README.md

@@ -342,6 +342,15 @@ average(1, 2, 3);
 
 </details>
 
+### _Uncategorized_
+
+<details>
+<summary>View contents</summary>
+
+* [`indexOfAll`](#indexofall)
+
+</details>
+
 ---
  ## 🔌 Adapter
 
@@ -5130,6 +5139,31 @@ yesNo('Foo', true); // true
 
 <br>[⬆ Back to top](#table-of-contents)
 
+---
+ ## _Uncategorized_
+
+### indexOfAll
+
+Returns all indices of `val` in an array. If `val` never occurs, returns `[-1]`.
+
+Use `Array.forEach()` to loop over elements and `Array.push()` to store indices for matching elements.
+Return `[-1]` if `length` of the array of indices is `0`, otherwise return the array of indices.
+
+```js
+const indexOfAll = (arr, val) => {
+  const indices = [];
+  arr.forEach((el, i) => el === val && indices.push(i));
+  return indices.length ? indices : [-1];
+};
+```
+
+```js
+indexOfAll([1, 2, 3, 1, 2, 3], 1); // [0,3]
+indexOfAll([1, 2, 3], 4); // [-1]
+```
+
+<br>[⬆ back to top](#table-of-contents)
+
 
 ## Collaborators