diff --git a/index.js b/index.js
index 3bb4d07..d206347 100644
--- a/index.js
+++ b/index.js
@@ -4,7 +4,66 @@
  * Depending on the operation, either add up all of the numbers or subtract all of the numbers, from left to right.
  * @returns {number} The result of either adding all numbers or subtracting all numbers, depending on the arguments added to the command line.
  */
-function calculator() {}
+// CLEAN CODE:
+function calculator() {
+    // assigning the operation if there's any
+    const command = process.argv[2];
+    // assigning the first number if there's number
+    const number = process.argv[3];
+    //converting the String type of number to the Number type
+    let result = Number(number);
+    
+    // if there's no operation
+    if (command === undefined) {
+        return "No operation provided...";
+    // if there's no number
+    } else if (number === undefined) {
+        return "No numbers provided...";
+    }
+    // looping from second number,
+    // because the first number is assigned to the variable result
+    for (let i = 4; i < process.argv.length; i++) {
+        if (command === 'plus') {
+            // adding to the first number
+            result += Number(process.argv[i]);
+        } else if (command === 'minus') {
+            // subtracting the first number
+            result -= Number(process.argv[i]);
+        } else {
+            // if the operation is not plus or minus
+            return `Invalid operation: ${command}`;
+        }
+    }
+    // return the total value;
+    return result;
+}
+
+
+// // MESSY CODE:
+// let result = 0;
+// function calculator() {
+//     if (process.argv[2] === undefined) {
+//        return "No operation provided...";
+//     } else if (process.argv[3] === undefined) {
+//        return "No numbers provided...";
+//     } else {
+//        let arr = [];
+//        for (let i = 3; i < process.argv.length; i++) {
+//            arr.push(parseInt(process.argv[i]));
+//        }
+//        for (let i = 0; i < arr.length; i++) {
+//            if (process.argv[2] === 'plus') {
+//                result = arr.reduce((a, b) => a + b);
+//            } else if (process.argv[2] === 'minus') {
+//                result = arr.reduce((a, b) => a - b);
+//            } else {
+//                return `Invalid operation: ${process.argv[2]}`;
+//            }
+//        }
+//     }
+//    return result;
+// }
+
 
 // Don't change anything below this line.
 module.exports = calculator;
diff --git a/package-lock.json b/package-lock.json
index 99b1c39..ce6f0ea 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5,6 +5,7 @@
   "requires": true,
   "packages": {
     "": {
+      "name": "8-0-javascript-on-your-machine-lab",
       "version": "1.0.0",
       "license": "ISC",
       "devDependencies": {