underscore/union()

解説 重複した値を省き配列を連結

_.union(Array, Array, ...)

Underscore.js 
(function(){
  let s1Array = [2, 3, 25, 12, 9];
  let s1Array02 = new Array(2, 4, 5);
  let s1Array03 = ["aaa", "bbb", "ccc"];
  var s1 = _.union(s1Array, s1Array02, s1Array03);
  s1 = _.sortBy(s1);
  console.log(s1);//[ 2, 3, 4, 5, 9, 12, 25, "aaa", "bbb", "ccc" ]
})();