Function flattenArray

docs/tests/v2/es6/js/sanddance.js:45992–46006

(array, filter, map, result)

function flattenArray(array, filter, map, result) {
  var index = -1;

  while (++index < array.length) {
    var value = array[index];

    if (Array.isArray(value)) {
      flattenArray(value, filter, map, result);
    } else if (filter(value)) {
      result.push(map(value));
    }
  }

  return result;
}

function countVertices(nestedArray) {
  var count = 0;