Array.splice is not a function

I am trying to remove an element from an array not marked with this bit of code.

function filterSearch() {
var cats = [];

$('.filter-by-type input[type="checkbox"]').change(function() {
  var cat = $(this).attr('name') + ', ';
   if(this.checked) {
      cats += cat;
   } else {
      cats.splice(cats.indexOf(cat), 1);
   }

  console.log(cats);
 });

}

filterSearch();

      

        
        
        
      

    

I am getting the error Uncaught TypeError: cats.splice is not a function

Basically, I want to add a value to the array cats[]

if the item is checked and removed if not set. Any help would be greatly appreciated.