How to generate a random weighted distribution of elements

Question

I would like to return an array which has a set of unique elements randomly distributed according to custom frequency. My real world use-case is the repetition of carousel i

Answer 1

To expand on a_gupta's answer:

function pick_bin(binProbabilities){     // e.g. [0.1, 0.3, 0.3, 0.3]
  var cumulative = [];                   // e.g. [0.1, 0.4, 0.7, 1]
  var accumulator = 0;

  // Iterating over an array with forEach:
  binProbabilities.forEach(function(item, index){
    var prob = Number(item);
    accumulator += prob;
    cumulative[index] = accumulator;
  })

  if(accumulator !== 1){
    throw new Error('Sum of binProbabilities must equal 1')
  }

  var n = binProbabilities.length;
  var rFloat = Math.random();

  // Iterating over an array with for:
  for(var i=0; i= rFloat){            // Found the first bin fitting the random number
      console.log(i);
      return i;
    }
  }
}

pick_bin([1]); // returns 0 every time
pick_bin([.5, .5]) // returns 0,1 50/50
pick_bin([0.1, 0.3, 0.3, 0.3])

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followup for your > 100% example, you can recalculate the weights to make them equal 1 (for a valid probability)

Desired weightings:     20% 50% 80% 10%
Sum these weights:      20 + 50 + 80 + 10 = 160
Divide each by the sum: 2/16, 5/16, 8/16, 1/16
Now they sum to 1