Flatten And Unique

flattenAndUnique.js

function isStringNumber(input) {
  return !!(typeof input === 'string' && input.match(/^\d+$/));
}

function includes(array, search) {
  return array.some(function(element) {
    if (typeof search === 'number' || isStringNumber(search)) {
      return search == element;
    } else {
      return search === element;
    }
  })
}

function flattenAndUnique(array) {
  var output = [];

  array.forEach(function(subarray) {
    subarray.forEach(function(element) {
      if (!includes(output, element)) {
        output.push(element);
      }
    })
  })

  return output;
}