Randome unique value.

/**
 * Return randome unique values from a array
 *
 * @param {A1:D10} data - Your dataset.
 * @param {5} amount  - number of values returned.
 * @return Unique values from input
 * @customfunction
 */
function RNDUNIQ(data, amount) {
  const arr1d = [].concat(...data);
  const result = [];
  const numbers = [];
  const arrLength = arr1d.length;

  do {
    const n = rand(arrLength);
    if (numbers.indexOf(n) < 0){
      numbers.push(n); }
  } while (numbers.length < amount)

    for ( var i = 0; i < amount; i++ ) {
      result.push(arr1d[numbers[i]]);
    }

  return result;

}

function rand(length) {
  return Math.floor(Math.random() * length);
}