added 66-plus-one-Javascript

Author: Chrislee1996

javascript/66-plus-one.js

@@ -0,0 +1,16 @@
+/**
+ * @param {number[]} digits
+ * @return {number[]}
+ */
+ var plusOne = function(digits) {
+    for (let i = digits.length-1 ; i >= 0 ; i--) {
+        if (digits[i] !== 9) {
+            digits[i]++
+            return digits
+        } else {
+            digits[i] = 0
+        }
+    }
+    digits.unshift(1)
+    return digits
+};