diff --git a/STEP2_1.js b/STEP2_1.js
new file mode 100644
index 0000000..be34d72
--- /dev/null
+++ b/STEP2_1.js
@@ -0,0 +1,48 @@
+const {PI} = Math
+
+function checkType(arr) {
+    for (let i = 0; i < arr.length; i++) {
+        if (typeof(arr[i]) !== "number") {
+            throw "please input Number data type";
+        }
+    }
+}
+
+function checkArgumentCount(arr, correctCount) {
+    if (arr.length !== correctCount) {
+        throw "please input correct number of arguments"
+    }
+}
+
+function circleArea(r) {
+    checkArgumentCount(arguments, 1);
+    checkType(arguments);
+
+    return PI * Math.pow(r, 2)
+}
+
+function squareArea(width, height) {
+    checkArgumentCount(arguments, 2);
+    checkType(arguments);
+
+    return width * height;
+}
+
+function trapezoidArea(x1, x2, h) {
+    checkArgumentCount(arguments, 3);
+    checkType(arguments);
+
+    return (x1 + x2) * h / 2
+}
+
+function cylinderArea(r, h) {
+    checkArgumentCount(arguments, 2);
+    checkType(arguments);
+
+    return (2 * PI * Math.pow(r, 2)) + 2 * PI * r * h
+}
+
+console.log(circleArea(3));
+console.log(squareArea(2, 7));
+console.log(trapezoidArea(6, 3, 3));
+console.log(cylinderArea(4, 6));
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