diff --git "a/\354\261\225\355\204\260_12/\354\230\244\355\230\234\354\204\261.md" "b/\354\261\225\355\204\260_12/\354\230\244\355\230\234\354\204\261.md"
new file mode 100644
index 0000000..d74a91b
--- /dev/null
+++ "b/\354\261\225\355\204\260_12/\354\230\244\355\230\234\354\204\261.md"
@@ -0,0 +1,40 @@
+# 함수형 반복
+
+## Map
+
+```js
+function map(arr, f) {
+    const newArr = []
+    for (const val of arr) {
+        newArr.push(f(val))
+    }
+    return newArr
+}
+```
+
+## Filter
+
+```js
+function filter(arr, f) {
+    const newArr = []
+    for (const val of arr) {
+        if (f(val)) newArr.push(val)
+    }
+    return newArr
+}
+```
+
+## Reduce
+
+```js
+function reduce(arr, init, f) {
+    let acc = init
+    for (const val of arr) {
+        acc = f(acc, val)
+    }
+    return acc
+}
+```
+
+* fold 라는 이름으로도 사용됨
+  + foldLeft, foldRight 같이 탐색 방향에 따른 버전도 있음