Parsing multiple arguments from the command line Node.js/js

Question

I'm trying to write a program that takes any number of command line arguments, in this case, strings and reverses them, then outputs them to the console. Here is what I have so far:

let CL = process.argv.slice(2);
let extract = CL[0];

function reverseString(commandInput) {
  var newString = "";
  for (var i = commandInput.length - 1; i >= 0; i--) {
    newString += commandInput[i];
  }
  return console.log(newString);
}

let call = reverseString(extract);

I can't figure out a way to make this work for multiple arguments in the command line such as:

node reverseString.js numberOne numberTwo

which would result in output like this:

enOrebmun owTrebmun

however it works fine for a single argument such as:

node reverseString.js numberOne

Not clear what result you're trying to end up with. Maybe CL.join(" ").reverse(). — jfriend00
– jfriend00, Commented Feb 17, 2019 at 3:00
let calls = CL.map(reverseString); then log them if you want like: console.log(calls.join("\n")); — ibrahim mahrir
– ibrahim mahrir, Commented Feb 17, 2019 at 3:01
You simply have to perform the operation for each item in CL - for (const x in CL) { console.log(reverseString(x)) } — Mulan
– Mulan, Commented Feb 17, 2019 at 3:04
you should change return console.log(newString) to return newString - console.log doesn't return anything. — Mulan
– Mulan, Commented Feb 17, 2019 at 4:08

adamrights · Accepted Answer · 2019-02-17 03:52:45Z

You need to run your reverseString() function on each of the argv[n...] values passed in. After correctly applying the Array.prototype.splice(2) function, which removes Array index 0 and 1 (containing the command (/path/to/node) and the /path/to/module/file.js), you need to iterate over each remaining index in the array.

The Array.prototype.forEach method is ideal for this, instead of needing a for loop or map. Below is using the OP code and is the minimal program (without much refactor) needed for desired output.

    let CL = process.argv.slice(2);

    function reverseString(commandInput) {
      var newString = "";
      for (var i = commandInput.length - 1; i >= 0; i--) {
        newString += commandInput[i];
      }
      return console.log(newString);
    }

    CL.forEach((extract)=>reverseString(extract))

Here is me running this code from the terminal:

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