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In this problem, you've to 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.

The current as well as new inventory will be in this format: var newInv = [[2, "Item1 Name"], [3, "Item2 Name"], [67, "Item3 Name"], [7, "Item4 Name"]];.

• Global Array object

You need to work through each item of the new inventory to see if it exists in the current inventory or not. Remember that the product name is stored as the second element of each sub-array: arr2[0][1] = "Bowling Ball".

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If the item exists, you need to add the quantity from the new inventory. If the item doesn't exist, you need to add the entire item.

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Return the completed inventory in alphabetical order.

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Solution ahead!

function updateInventory(arr1, arr2) {

    // Variable for location of product
    var index;

    // A helper method to return the index of a specified product (undefined if not found)
    var getProductIndex = function (name) {
        for (var i = 0; i < this.length; i++) {
            if (this[i][1] === name) {
                return i;
            }
        }
        return undefined;
    }

    // For each item of the new Inventory
    for (var i = 0; i < arr2.length; i++) {

        // Invoke our helper function using arr1 as this
        index = getProductIndex.call(arr1, arr2[i][1]);

        // If the item doesn't exist
        if (index === undefined) {
            // Push the entire item
            arr1.push(arr2[i]);
        } else {
            // Add the new quantity of the current item
            arr1[index][0] += arr2[i][0];
        }

    }

    // Sort alphabetically, by the product name of each item
    arr1.sort(function (a, b) {
        if (a[1] > b[1]) {
            return 1;
        }
        if (a[1] < b[1]) {
            return -1;
        }
        return 0;
    });

    return arr1;
}

// test here
// 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(curInv, newInv);

🚀 Run Code

• The variable index stores the location (index) of a product.
• The helper function getProductIndex() returns the index of a specified product. It iterates through each element of the array that it is called on until it can find the name parameter. If the product is not found in the inventory, undefined is returned.
• Then, each item in the new inventory (delivery) is worked through:
  • index is set to the result of invoking the helper function i.e., search the new inventory for that product name and return it's index.
  • If the item is found, quantity of the product is added to the quantity of the same product in current inventory.
  • If the item is not found, the entire product (name and quantity) is added to the current inventory.
• The updated inventory, arr1, is then sorted by product name (held in arr1[x][1]).
• The final - updated as well as sorted array is then returned.

• JS For Loops Explained
• this keyword
• array.length
• JS Array Prototype Push
• JS Array Prototype Sort

function updateInventory(arr1, arr2) {
  // All inventory must be accounted for or you're fired!

  var index;
  var arrCurInvName = []; // Names of arr1's items
  var arrNeInvName = []; // Names of arr2's items

  // Same as using two for loops, this takes care of increasing the number of stock quantity.
  arr1.map(function(item1) {
    return arr2.map(function(item2) {
      if (item1[1] === item2[1]) {
        item1[0] = item1[0] + item2[0]; //Increase number of stock
      }
    });
  });

  // Get item's name for new Inventory
  arr2.map(function(item) {
    arrNeInvName.push(item[1]);
  });

  // Get item's name for Current Inventory
  arr1.map(function(item) {
    arrCurInvName.push(item[1]);
  });

  // Add new inventory items to current inventory.
  arrNeInvName.map(function(item) {
    if (arrCurInvName.indexOf(item) === -1) {
      index = arrNeInvName.indexOf(item);
      arr1.push(arr2[index]);
    }
  });

  // Sort the array alphabetically using the second element of the array as base.
  arr1.sort(function(currItem, nextItem) {

    //Ternary function to avoid using if else
    return currItem[1] > nextItem[1] ? 1 : -1;
  });

  return arr1;
}

// test here
// 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(curInv, newInv);

🚀 Run Code

• The variable index stores the location (index) of a product.
• arrCurInvName has the names of arr1's items.
• arrNeInvName has the names of arr2's items.
• arr1.map(function(item1)) takes care of items already existing in inventory i.e., it increases the quantity in the inventory.
• Next, arr2.map(function(item)) and arr1.map(function(item)) get the names of items for the new and current inventory respectively.
• arrNeInvName.map(function(item)) handles items which don't already exist in inventory i.e., it adds new items to the inventory.
• The updated array arr1 is then sorted alphabetically by product name (held in arr1[x][1]) and returned.

• JS Array Prototype Map
• JS Array Prototype IndexOf
• JS Ternary

function updateInventory(arr1, arr2) {
  var flag = 0;
  arr2.forEach(function(item) {
    flag = 0;
    arr1.forEach(function(list) {
      // If the product is already present, increase the quantity
      if(item[1] === list[1]) {
        list[0] += item[0];
        flag = 1;
      }
    });
    //If not already present, add the product
    if(flag === 0)
      arr1.push(item);
  });

  //Return the sorted inventory in alphabetical order by product name
  return arr1.sort(function(a, b) {
    return a[1] > b[1] ? 1 : -1;
  });
}

// test here
// 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(curInv, newInv);

🚀 Run Code

• The variable flag is a flag variable which checks whether a product exists in the inventory. A flag variable, in its simplest form, is a variable you define to have one value until some condition is true, in which case you change the variable's value.
• arr2.forEach(function(item)) iterates through each item in the new delivery:
  • If the product is already present, it's quantity is simply updated and flag is made 1.
  • If the product is new i.e., flag is 0, it is added to the inventory using the push() method.
• The updated array arr1 is then sorted alphabetically by product name.

• JS Array Prototype ForEach

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Thanks @guyjoseph @Rafase282 @anuragaryan for your help with Algorithm: Inventory Update

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