Inventory Update: Compare and update the inventory stored in a 2D array against a second 2D array of a fresh delivery. Update the current existing inventory item quantities (in arr1). If an item cannot be found, add the new item and quantity into the inventory array. The returned inventory array should be in alphabetical order by item.

inventoryUpdate.js

function updateInventory(arr1, arr2) {
    
    let updatedArr = [];

    if(arr1 === []){
        updatedArr = arr2;
    }else if(arr2 === []) {
        updatedArr = arr1;
    }else{
        let newItemArr = [];
        for(let i=0; i<arr2.length; i++){
            let flag = false;
            for(let j=0; j<arr1.length; j++){
                if(arr2[i][1] === arr1[j][1]){
                    flag = true;
                    arr1[j][0] += arr2[i][0];
                }
            }
            if(!flag){
                newItemArr.push(arr2[i]);
            }
        }       
        updatedArr = arr1.concat(newItemArr)
    }
    
    for(let i=0; i<updatedArr.length; i++){
        updatedArr[i].reverse(); //prepare for sorting alphabetical order
    }
    updatedArr.sort(); //sort according to alphabetical order by item.
    for(let i=0; i<updatedArr.length; i++){
        updatedArr[i].reverse(); //reverse back to original format after sorting
    }
    return updatedArr;
}

// Example inventory lists

var curInv = [
    [21, "Bowling Ball"], [2, "Dirty Sock"], [1, "Hair Pin"], [5, "Microphone"]
];

var newInv = [
    [2, "Hair Pin"], [3, "Half-Eaten Apple"], [67, "Bowling Ball"], [7, "Toothpaste"]
];

/*
updateInventory([[21, "Bowling Ball"], [2, "Dirty Sock"], [1, "Hair Pin"], [5, "Microphone"]], []) should return [[21, "Bowling Ball"], [2, "Dirty Sock"], [1, "Hair Pin"], [5, "Microphone"]].
Passed
updateInventory([], [[2, "Hair Pin"], [3, "Half-Eaten Apple"], [67, "Bowling Ball"], [7, "Toothpaste"]]) should return [[67, "Bowling Ball"], [2, "Hair Pin"], [3, "Half-Eaten Apple"], [7, "Toothpaste"]].
Passed
updateInventory([[0, "Bowling Ball"], [0, "Dirty Sock"], [0, "Hair Pin"], [0, "Microphone"]], [[1, "Hair Pin"], [1, "Half-Eaten Apple"], [1, "Bowling Ball"], [1, "Toothpaste"]]) should return [[1, "Bowling Ball"], [0, "Dirty Sock"], [1, "Hair Pin"], [1, "Half-Eaten Apple"], [0, "Microphone"], [1, "Toothpaste"]].
 */
updateInventory(curInv, newInv);