index.js

/**
 * The function below has no parameters. Instead, access the arguments from the command line.
 * The first argument passed after the filename should be either "plus" or "minus", which represents the kind of calculation that will be done. Every argument afterwards should be a number.
 * 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() {
    let result;

   if (process.argv.length <= 2) {
    return "No operation provided...";
   }
   else if (process.argv.length == 3) {
    return "No numbers provided...";
   }
   else {
        
        result = Number(process.argv[3]);

        switch(process.argv[2]){
            case "plus":
                for (let i =4; i < process.argv.length; i++){
                    result += Number(process.argv[i])
                }
                break;
            case "minus":
                for (let i =4; i < process.argv.length; i++){
                    result -= Number(process.argv[i])
        }
        break;
    default:
        return `Invalid operation: ${process.argv[2]}`;
   }
}
return result;

}

// Don't change anything below this line.
module.exports = calculator;