freeCodeCamp Intermediate Algorithm Scripting: Sorted Union

uniteUnique.js

// Write a function that takes two or more arrays and returns a new 
// array of unique values in the order of the original provided arrays.

// In other words, all values present from all arrays should be included 
// in their original order, but with no duplicates in the final array.

// The unique numbers should be sorted by their original order, but the 
// final array should not be sorted in numerical order.


function uniteUnique(arr) {
  let base=arguments[0];
  let rest = [];
  for (let i=1; i<arguments.length; i++) {
    rest.push(arguments[i]);
  }

  rest.map(nextList => {
    nextList.map(item => {
      if (base.indexOf(item) < 0) { 
        base.push(item);
      }
    });
  });
  return base;
}

uniteUnique([1, 3, 2], [5, 2, 1, 4], [2, 1]); // [1, 3, 2, 5, 4]
uniteUnique([1, 3, 2], [1, [5]], [2, [4]]); // [1, 3, 2, [5], [4]]
uniteUnique([1, 2, 3], [5, 2, 1]); // [1, 2, 3, 5]
uniteUnique([1, 2, 3], [5, 2, 1, 4], [2, 1], [6, 7, 8]); // [1, 2, 3, 5, 4, 6, 7, 8]