diff --git a/hyewon/4-exchangeRate/README.md b/hyewon/4-exchangeRate/README.md
new file mode 100644
index 0000000..0edd771
--- /dev/null
+++ b/hyewon/4-exchangeRate/README.md
@@ -0,0 +1,58 @@
+# 목차
+- `fetch()`
+- swap
+
+## `fetch()`
+- - -
+- Fetch API 를 이용하면 Request/Response 를 조작하는 것이 가능하다.
+- fetch() 메소드는 첫번째 인자로 URL, 두번째 인자로 option 객체를 받고, Promise 객체를 반환한다.
+반환된 객체는 API 호출이 성공했을 경우에는 response 객체를 resolve 하고, 실패했을 경우에는 error 객체를 reject 한다.
+
+### 내 코드
+```javascript
+fetch("https://v6.exchangerate-api.com/v6/0c8fbd2c3ca43caf99612cff/latest/USD")
+ .then((response) => { return response.json() })
+ .then((response) => {
+ // 생략
+ })
+```
+그런데 왜 첫번째 then() 에서 바로 response.json() 을 사용하지 않고 그 다음 then() 으로 넘겨줘야만 하는지 잘 모르겠다...
+
+## swap
+- - -
+```javascript
+//JavaScript program to swap two variables
+
+//take input from the users
+let a = prompt('Enter the first variable: ');
+let b = prompt('Enter the second variable: ');
+
+//using destructuring assignment
+[a, b] = [b, a];
+
+console.log(`The value of a after swapping: ${a}`);
+console.log(`The value of b after swapping: ${b}`);
+```
+↑ 구조 분해 할당을 이용한 변수 값 교환
+
+### 내 코드
+```javascript
+function swap() {
+ const firIndex = $firstSelect.selectedIndex
+ const secIndex = $secondSelect.selectedIndex
+ $firstSelect.options[secIndex].selected = true
+ $secondSelect.options[firIndex].selected = true
+ [$firstSelect, $secondSelect] = [$secondSelect, $firstSelect]
+ calculate()
+}
+```
+
+## 참조
+- - -
+- `fetch()`
+https://developer.mozilla.org/ko/docs/Web/API/Fetch_API/Using_Fetch
+https://developer.mozilla.org/en-US/docs/Web/API/fetch
+https://www.daleseo.com/js-window-fetch/
+- swap
+https://www.programiz.com/javascript/examples/swap-variables
+https://developer.mozilla.org/ko/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment
\ No newline at end of file
diff --git a/hyewon/4-exchangeRate/img/money.png b/hyewon/4-exchangeRate/img/money.png
new file mode 100644
index 0000000..9318522
Binary files /dev/null and b/hyewon/4-exchangeRate/img/money.png differ
diff --git a/hyewon/4-exchangeRate/index.html b/hyewon/4-exchangeRate/index.html
new file mode 100644
index 0000000..63b4043
--- /dev/null
+++ b/hyewon/4-exchangeRate/index.html
@@ -0,0 +1,142 @@
+
+
+
+
+
+
+ Exchange Rate Calculator
+
+
+
+
+
Exchange Rate Calculator
+
Choose the currency and the amounts to get the exchange rate