find.js

function existsInArray(array, items) {
  var all = true;
  for (i = 0; i < items.length; i++) {
    all &= array.indexOf(items[i]) !== -1;
  }

  return all;
}

if (!existsInArray(['a', 'c'], ['c'])) {
  console.log('No');
} else {
  console.log('Yes');
}

if (existsInArray(['a', 'c'], ['a', 'c']) === true) {
  console.log('Yes!');
} else {
  console.log('No!');
}