diff --git a/javascript/0438-find-all-anagrams-in-a-string.js b/javascript/0438-find-all-anagrams-in-a-string.js
new file mode 100644
index 000000000..2a22e402d
--- /dev/null
+++ b/javascript/0438-find-all-anagrams-in-a-string.js
@@ -0,0 +1,42 @@
+/**
+ * @param {string} s
+ * @param {string} p
+ * @return {number[]}
+ */
+var findAnagrams = function (s, p) {
+    const charMap = new Map();
+    let matches = 0;
+    const matchIdx = [];
+
+    for (const char of p) {
+        const charCount = charMap.get(char) || 0;
+        charMap.set(char, charCount + 1);
+    }
+
+    let leftWindow = 0;
+    for (let rightWindow = 0; rightWindow < s.length; rightWindow++) {
+        const rightChar = s[rightWindow];
+        if (charMap.has(rightChar)) {
+            const rightCharCount = charMap.get(rightChar);
+            charMap.set(rightChar, rightCharCount - 1);
+            if (charMap.get(rightChar) === 0) {
+                matches++;
+            }
+        }
+        if (rightWindow >= p.length) {
+            const leftChar = s[leftWindow];
+            if (charMap.has(leftChar)) {
+                const leftCharCount = charMap.get(leftChar);
+                charMap.set(leftChar, leftCharCount + 1);
+                if (leftCharCount === 0) {
+                    matches--;
+                }
+            }
+            leftWindow++;
+        }
+        if (matches === charMap.size) {
+            matchIdx.push(leftWindow);
+        }
+    }
+    return matchIdx;
+};