Get a collection randomly from a array using javascript

Question

var ramdomCharacters = ["a", "c", "z", "d", "f", "i", "u"];

I want to extract a subset ramdomly from ramdomCharacters, which has a random length and non-repeated item. Like this:

subset = ["c", "f", "i"]

or

subset = ["a", "u"]

Answer 1

One possible way is to randomise the array and extract first n elements:

var randomCharacters = ['a', 'c', 'z', 'd', 'f', 'i', 'u'];

var clone = [].slice.call(randomCharacters),   // clone not to alter the original
    n = Math.random() * clone.length + 1,      // `n` may vary upon your needs
    subset = clone.sort(function() {
        return 0.5 - Math.random();            // shuffle array
    }).slice(0, n);                            // slice first `n` elements

console.log(subset);

Answer 2

You could try:

var randomCharacters = ['a', 'c', 'z', 'd', 'f', 'i', 'u'];
var subset=[];
while (randomCharacters.length>0)
  {
    dummy=randomCharacters.pop();
    if (Math.random()<0.5) subset.push(dummy);
  }
document.write(subset);

This varies from the previous answer in that (1) randomCharacters ends up as [], (2) the final value of 'subset' might be [] and (3), although random, the order of 'subset' is effectively the same as the reverse order of randomCharacters.