Whew...Done

index.js

@@ -4,7 +4,29 @@
  * 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() {}
+function calculator(){
+    if(process.argv.length < 3){  // Not adding anything since first two arguments are not numbers, they are strings
+        return 'No operation provided...'
 
+    } else if (process.argv.length < 4) { // 
+        return "No numbers provided..."
+
+    } else if (process.argv[2] === 'plus'){ 
+        let total = 0 
+        for (let i = 3; i < process.argv.length; i++){ // Looping to find if the operations strictly equals 'plus'
+            total += Number (process.argv[i]) //
+        }
+        return total 
+
+    } else if (process.argv[2] === 'minus'){
+        let total = process.argv[3]
+        for (let i = 4; i < process.argv.length; i++){
+            total -= Number (process.argv[i])
+        }
+        return total
+    } else {
+        return `Invalid operation: modulo`
+    }
+}
 // Don't change anything below this line.
 module.exports = calculator;