Terminal command 'ls' using Node

ls.js

const fs = require('fs');

fs.readdir('.', 'utf8', (err, files) => {
  if ( err ) {
    console.log('Error: ', err);
    return;
  }

  let largestLength = files.slice().sort((a,b) => b.length - a.length)[0].length;
  let columns = Math.floor( process.stdout.columns / largestLength );

  let formattedString = '';
  let j = 1;
  files.sort((a,b) => b[0] - a[0]);
  for ( let k = 0; k < files.length; k++ ) {
    formattedString += `${files[k]}`.padEnd(process.stdout.columns / columns);
    if ( ++j === columns ) {
      console.log(formattedString.trim());
      j = 0;
      formattedString = '';
    }
  }
});