Generate random numbers that are unique and writing that to a CSV document.

random-number-csv.js

/*
 * System for generating x number of unique numbers and writing that to a CSV 
 * document. Good for competitions or anything requiring true unique numbers.
 * Also an interesting exercise for Node/Javascript perf.
 */
const fs = require('fs');
const numbers = [];
const start = 111111111; // We don't want any leading 0's
const end = 999999999;
const amount = 3000000;
const step = Math.floor((end-start)/amount);
const padding = 9;
const file = fs.createWriteStream('numbers.csv');

function toText(number) {
  const toPad = padding - number.toString().length;
  let paddingString = '';

  for (let c=0; c<toPad; c++) {
    paddingString += '0';
  }

  return number.toString()+''+paddingString;
};

function shuffle(array) {
    let counter = array.length;

    // While there are elements in the array
    while (counter > 0) {
        // Pick a random index
        let index = Math.floor(Math.random() * counter);

        // Decrease counter by 1
        counter--;

        // And swap the last element with it
        let temp = array[counter];
        array[counter] = array[index];
        array[index] = temp;
    }

    return array;
}

function convertArraytoText(arr) {
  let numberArray = [];

  for (let c=0; c<arr.length; c++) {
    numberArray.push(toText(arr[c]));
  }

  return numberArray;
}

// Create our array to shuffle
for (let c=1; c<=amount; c++) {
  numbers.push(toText(c*step));

  // console.log(c+'> '+toText(c*step));
}

// Shuffle array
const shuffledNumbers = shuffle(numbers);

// Write each entry to file
shuffledNumbers.forEach(function(v) {
  file.write(v + '\n');
});

file.end();