Get unique elements of an Array

unique.js

// Another useful reducer
// 
// Get unique values of a 1d array
function unique (a, b) {
  if (a.indexOf(b) < 0) a.push(b)
  return a
}

// Very simple use case
var arr = [1, 5, 7, 2, 2, 3, 3, 4, 5, 5, 52, 4, 1, 2, 9, 1, 3, 5]

// Reduce it
arr.reduce(unique, []) // <= note the [] param

// Produces:
[1, 5, 7, 2, 3, 4, 52, 9]

// This can also be easily accomplished with Array#filter,
// but I really like the elegance of this reduce approach