diff --git a/solutions/leetcode/258-add-digits/index.js b/solutions/leetcode/258-add-digits/index.js
new file mode 100644
index 0000000..d44fc2c
--- /dev/null
+++ b/solutions/leetcode/258-add-digits/index.js
@@ -0,0 +1,20 @@
+const Assert = require('assert')
+
+/**
+ * @param {number} num
+ * @return {number}
+ */
+function addDigits(num) {
+    var str;
+    while (num > 9) {
+        str = num + "";
+        num = 0;
+        for (var i = 0, j = str.length; i < j; i++) {
+            num += Number(str[i]);
+        }
+    }
+    return num;
+};
+
+Assert.equal(addDigits(38), 2)
+Assert.equal(addDigits(64), 1)
\ No newline at end of file