Array Map: map()

map() is used to create a new array by doing something to each item in the original array.

var items = [
    {
        "index": 1,
        "item_id": "41499884552324",
        "product_id": "7135045746820",
        "variant_id": "41499884552324",
        "item_name": "7 Shakra Bracelet",
        "quantity": 2,
        "price": 5400,
        "discount": 0,
        "item_category": "Bracelet",
        "item_brand": "Company 123",
        "item_variant": "Blue"
    },
    {
        "index": 2,
        "item_id": "41499881439364",
        "product_id": "7135044173956",
        "variant_id": "41499881439364",
        "item_name": "Black Leather Bag",
        "quantity": 1,
        "price": 3800,
        "discount": 0,
        "item_brand": "partners-demo"
    }
];

var contentIds = items.map(function(item) {
  var itemId = item.item_id;
  return itemId;
});

console.log(contentIds); // ['41499884552324', '41499881439364']

var items = [
    {
        "index": 1,
        "item_id": "41499884552324",
        "product_id": "7135045746820",
        "variant_id": "41499884552324",
        "item_name": "7 Shakra Bracelet",
        "quantity": 2,
        "price": 5400,
        "discount": 0,
        "item_category": "Bracelet",
        "item_brand": "Company 123",
        "item_variant": "Blue"
    },
    {
        "index": 2,
        "item_id": "41499881439364",
        "product_id": "7135044173956",
        "variant_id": "41499881439364",
        "item_name": "Black Leather Bag",
        "quantity": 1,
        "price": 3800,
        "discount": 0,
        "item_brand": "partners-demo"
    }
];

var remarketingItems = items.map(function(item) {
  var remarketingItem = {
    id: item.item_id,
    google_business_vertical: 'retail'
  }
  
  return remarketingItem;
});

console.log(remarketingItems); // log result

var items = [
    {
        "index": 1,
        "item_id": "41499884552324",
        "product_id": "7135045746820",
        "variant_id": "41499884552324",
        "item_name": "7 Shakra Bracelet",
        "quantity": 2,
        "price": 5400,
        "discount": 0,
        "item_category": "Bracelet",
        "item_brand": "Company 123",
        "item_variant": "Blue"
    },
    {
        "index": 2,
        "item_id": "41499881439364",
        "product_id": "7135044173956",
        "variant_id": "41499881439364",
        "item_name": "Black Leather Bag",
        "quantity": 1,
        "price": 3800,
        "discount": 0,
        "item_brand": "partners-demo"
    }
];

var contents = items.map(function(item) {
  var content = {
    id: item.item_id,
    quantity: item.quantity
  }
  
  return content;
});

console.log(contents); // log result