Preventing Random Operation From Returning Same Value Twice In Javascript

I'm very new to coding, and working on my first Javascript project. I'm trying to create a small random character generator which randomly selects a setting, and character archetyp

Solution 1:

You can shuffle the array (e.g. using the Fisher-Yates shuffle), then just iterate one-by-one over the shuffled array. When you get to the end of one, just shuffle it again.

Solution 2:

You can use following method for shuffling:

functionshuffle(o){ //v1.0for(var j, x, i = o.length; i; j = parseInt(Math.random() * i), x = o[--i], o[i] = o[j], o[j] = x);
    return o;
};
shuffle(setting);
 shuffle(Archetype);

reference

Solution 3:

I would create an additional index of the array that I could loop over to get references. This will create a constant random order of all elements in the array, that when having traversed all elements would reset to the first one and traverse again in the same order.

This method is compatible with a shuffled copy as well, such as is described in any other answer. And you can use a better shuffling algorithm, this one is naive. Since your arrays are so small however, the performance increase will be minimal. If you want to make a shuffled copy you won't need to map the index, you only need to create the copy when creating the object.

This code is not tested. I'm not sure about the interval of Math.random, but I'm assuming 0 < x < 1 here:

var RandomWalk = function(items) {
  var self = this;
  if (!items.length) {
    // throw some error
  }

  this.index = 0;
  this.index_map = (function(items) {
    var map = [], i = 0;
    while(map.length < items.length) {
      i = Math.floor(Math.random() * items.length);
      if (map.indexOf(i) === -1) {
        map.push(i);
      }
    }
    return map;
  })(items); // Note that this function is evaluated, index_map is not a functionthis.index_max = this.index_map.length - 1;
  this.next = function() {
    var r = self.index_map[self.index];
    if (self.index == self.index_max) {
      self.index = 0;
    } else {
      self.index += 1;
    }
    return r;
  }
  returnthis;
}

Then you'd do something like this:

// define settings and archetypevar archetype_walk = new RandomWalk(archetype);
function resetSettingAndArchetype()
{
  ...
  var arch_index = archetype_walk.next(),
      arch = archetypes[arch_index]
  // arch is in ['Ninja', 'Samurai', 'Druid' ...]

By the way, 'Archetype' might be a bad variable name. It looks like a function. I use 'archetype' here.