Merge count snippets

content/redirects.yaml

@@ -2914,3 +2914,6 @@
 - from: /js/s/uncached-module-require
   to: /js/s/reload-module
   status: 301!
+- from: /js/s/count-substrings
+  to: /js/s/count-occurences
+  status: 301!

content/snippets/js/s/count-occurrences.md

@@ -1,19 +1,46 @@
 ---
-title: Count occurrences
-type: snippet
+title: Count the occurrences of a value in a JavaScript array or string
+shortTitle: Count occurrences
+type: story
 language: javascript
-tags: [array]
+tags: [array,string]
 cover: dark-leaves-4
-dateModified: 2020-10-18
+excerpt: Given a value, find out how many times it appears in an array or string.
+dateModified: 2024-05-14
 ---
 
-Counts the occurrences of a value in an array.
+I've often had a need to count the occurrences of a specific value in an array or a string. While both of these use-cases seem simple, there are a few intricacies that you need to be aware of.
 
-- Use `Array.prototype.reduce()` to increment a counter each time the specific value is encountered inside the array.
+## Count value occurrences in an array
+
+`Array.prototype.reduce()` provides the most straightforward way to count the occurrences of a value in an **array**. Simply increment a counter each time the specific value is encountered inside the array and return the final count.
 
 ```js
 const countOccurrences = (arr, val) =>
   arr.reduce((a, v) => (v === val ? a + 1 : a), 0);
 
 countOccurrences([1, 1, 2, 1, 2, 3], 1); // 3
 ```
+
+> [!NOTE]
+>
+> You can count the **occurrences of all values** in an array, as described in the [previous article](/js/s/count-grouped-elements).
+
+## Count value occurrences in a string
+
+Counting the occurrences of a value in a **string** is a bit more complex than in an array. You can use `Array.prototype.indexOf()` to look for the value in the string and increment a counter each time it's found. Update the index to the next position after the value is found and continue the search until the value is no longer found, using a `while` loop. The loop terminates when `Array.prototype.indexOf()` returns `-1`.
+
+```js
+const countSubstrings = (str, searchValue) => {
+  let count = 0,
+    i = 0;
+  while (true) {
+    const r = str.indexOf(searchValue, i);
+    if (r !== -1) [count, i] = [count + 1, r + 1];
+    else return count;
+  }
+};
+
+countSubstrings('tiktok tok tok tik tok tik', 'tik'); // 3
+countSubstrings('tutut tut tut', 'tut'); // 4
+```