Storing same key and different values in JavaScript array and Matching with a key value pair

Question

     $(document).on('change', '.units', function () {
            var obj = $(this);
            unit_id = parseInt($(this).val());
            var item_array = [];
            var unit_array = [];
            var units = $(".units");
            var items = $(".items");

            $('#used_items tr').each(function () {
                $(this).find('.items').each(function () {
                    item_array.push($(this).val());
                });
                $(this).find('.units').each(function () {
                    unit_array.push($(this).val());
                });
            });
            var item_unit_associative_array = [];
            for (var i = 0; i < units.length; i++) {
                if (item_unit_associative_array[item_array[i]] == unit_array[i]) {
                    obj.val('');
                    return alert("Given Item Unit Already Selected");
                }
                else {
                    item_unit_associative_array[item_array[i]] = unit_array[i];
                }
            }
            console.log(item_unit_associative_array););

From item_array and unit_array I want to build new object like

var item_unit_associative_array=[1:12, 1:13 ,1:14,2:10];

and finally want to check an object consists of key:value like

var test ={1:12}

is exists or not in the item_unit_associative_array

Answer 1

I think you need to nest two layers of objects. See the comments for the structure:

var items = [ 1,  1,  1,  2];
var units = [12, 13, 14, 10];

// Create the object like so:
// { 
//   1: { 12: true, 13: true, 14: true },
//   2: { 10: true }
// }
var itemUnitAssociativeObject = {};
units.forEach(function(unitId, i) {
  var itemId = items[i];  
  if (!itemUnitAssociativeObject[itemId]) {
    itemUnitAssociativeObject[itemId] = {};
  }
  
  itemUnitAssociativeObject[itemId][unitId] = true;
});

console.log("1:13", test(1, 13));
console.log("1:10", test(1, 10));
console.log("2:10", test(2, 10));

function test(item, unit) {
   return !!(itemUnitAssociativeObject[item] &&
     itemUnitAssociativeObject[item][unit]);
}
  

If you don't like the nesting and the way it complicates your test, you can also "stringify" the item-unit id combination:

var items = [ 1,  1,  1,  2];
var units = [12, 13, 14, 10];

// Create the object like so:
// { 
//   "1:12": true,
//   "1:13": true, // etc.
// }
var map = items.reduce(function(map, itemId, i) {
  var id = itemId + ":" + units[i];
  map[id] = true;
  return map;
}, {});

console.log("1:13", map["1:13"]);
console.log("1:10", map["1:10"]);
console.log("2:10", map["2:10"]);