There may not be an unambiguous answer to which item occurs the most times. Here is how you can get the item counts in a functional style:
x.reduce(function(counts, key) {
if(!counts.hasOwnProperty(key))
counts[key] = 0
counts[key] = counts[key] + 1
return counts }, {})
Returns {"water": 3, "land": 4, "forest": 1}