Inventory Update Advanced Algorithm

Inventory_Update

// I am a fucking savage. 

function updateInventory(arr1, arr2){
    var merged = arr1.concat(arr2);

    var JSON_merged = {};

// utilizes fact that objects can not have repeating properties with the same name
// to filter out duplicates
    // will retain the last seen duplicate element during loop
    // newInv.concat(curInv) retains current inventory duplicate item and item count
    // curInv.concat(newInv) retains new inventory duplicate item and item count

    for(var i in merged){
        JSON_merged[merged[i][1]] = merged[i][0];
    }


// once the list is merged loop through the original inventory and the new duplicate-filtered
// JSON_merged object. For each matching pair check if the JSON_merged value is the same
// as the curInv item count. If it is the same then skip it, if they are different then
// update the count by adding the new count stored in the JSON_merged object
// and the old count stored in the curInv array
    for(i in arr1){
        for(var j in JSON_merged){
            if(arr1[i][1] === j){
                if(arr1[i][0] !== JSON_merged[arr1[i][1]]){
                    JSON_merged[arr1[i][1]] = JSON_merged[arr1[i][1]] + arr1[i][0];
                }
            }
        }
    }

    merged = []; // clear merged array to push duplicate-filtered elements back into it


// push object properties into array in original format
    // original format: [item count, 'item']
    for(var prop in JSON_merged){
        if(JSON_merged.hasOwnProperty(prop)){
            merged.push([JSON_merged[prop], prop]);
        }
    }

// sorting alphabetically based on item name, arr[x][1]
    function sorting_hat(a,b){
        return a[1].localeCompare(b[1]);
    }

    return merged.sort(sorting_hat);
}