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() {
    
    if(process.argv[2]=== `plus`){
        let sum = 0
        if(!parseInt(process.argv[3]) || !process.argv[3]){
            return "No numbers provided..."
          } else{  
             for (let i = 3; i < process.argv.length; i++) {
            sum += parseInt(process.argv[i])
         }
        }
          return sum
      }
      
    if(process.argv[2]===`minus`){
          let sum = process.argv[3]
          for(let i = 4; i < process.argv.length; i++){
             sum -= parseInt(process.argv[i])
          }
          return sum
      } 
    if(!process.argv[2]){
        return "No operation provided..."
    }
    
    if(process.argv[2]!=='plus' || process.argv[2]!== 'minus'){
        return "Invalid operation: modulo"
    }
}
// Don't change anything below this line.
module.exports = calculator;