diff --git a/snippets/transform.md b/snippets/transform.md
new file mode 100644
index 000000000..de8d1236d
--- /dev/null
+++ b/snippets/transform.md
@@ -0,0 +1,17 @@
+### transform
+
+Applies a function against an accumulator and each key in the object (from left to right).
+
+Use `Object.keys(obj)` to iterate over each key in the object, `Array.reduce()` to call the apply the specified function against the given accumulator.
+
+```js
+const transform = (obj, fn, acc) =>
+  Object.keys(obj).reduce((a, k) => fn(a, obj[k], k, obj), acc);
+```
+
+```js
+transform({ 'a': 1, 'b': 2, 'c': 1 }, (r, v, k) => {
+  (r[v] || (r[v] = [])).push(k);
+  return r;
+}, {}); // { '1': ['a', 'c'], '2': ['b'] }
+```
diff --git a/tag_database b/tag_database
index d9ad2a94e..e70eef4a2 100644
--- a/tag_database
+++ b/tag_database
@@ -181,6 +181,7 @@ tomorrow:date
 toOrdinalSuffix:utility,math
 toSafeInteger:math
 toSnakeCase:string,regexp
+transform:object,array
 truncateString:string
 truthCheckCollection:object,logic,array
 unescapeHTML:string,browser