Generate unique random numbers in a custom code block for Voiceflow

voiceflow_random_number.js

// Define number of choices available.
// Generated options: 0.. < num_max
const num_max = 5;

// Randomize array in-place using Durstenfeld shuffle algorithm
// Based on: https://stackoverflow.com/questions/2450954/how-to-randomize-shuffle-a-javascript-array
function shuffleArray(array) {
    for (var i = array.length - 1; i > 0; i--) {
        var j = Math.floor(Math.random() * (i + 1));
        var temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }
}

if (num_available === 0 || num_available.length === 0) {
  // First run / no numbers left
  // -> Fill array with shuffled options
  num_available = Array.from(Array(num_max).keys());
  shuffleArray(num_available);
}

// Select random option
num_now = num_available.pop();