A complete working example of all the uses of cursor for this article: https://itnext.io/searching-in-your-indexeddb-database-d7cbf202a17

IndexedDB with cursor complete example.js

const invoices = [
  { invoiceId: "c1-5b", vendor: "GE", paid: true },
  { invoiceId: "a", vendor: "GE", paid: false },
  { invoiceId: "-7c", vendor: "Whirlpool", paid: true },
  { invoiceId: "b", vendor: "Bosch", paid: true },
  { invoiceId: "9b54-dbdd", vendor: "Bosch", paid: false },
  { invoiceId: "2cac788-", vendor: "Whirlpool", paid: true },
  { invoiceId: "99cd9c14", vendor: "Bosch", paid: false },
  { invoiceId: "a1854b-14b", vendor: "Frigidaire", paid: false },
  { invoiceId: "43b76a75", vendor: "Bosch", paid: true },
  { invoiceId: "95b971959", vendor: "GE", paid: false }
];

const invoiceItems = [
  { invoiceId: "c1-5b", row: 0, item: "Table", price: 11822 },
  { invoiceId: "c1-5b", row: 1, item: "Recliner", price: 5296 },
  { invoiceId: "a", row: 0, item: "Table", price: 13162 },
  { invoiceId: "a", row: 1, item: "Dryer", price: 4129 },
  { invoiceId: "a", row: 2, item: "Refrigerator", price: 6930 },
  { invoiceId: "-7c", row: 0, item: "Dishwasher", price: 746 },
  { invoiceId: "-7c", row: 1, item: "Refrigerator", price: 12209 },
  { invoiceId: "-7c", row: 2, item: "Dryer", price: 12981 },
  { invoiceId: "-7c", row: 3, item: "Dryer", price: 6852 },
  { invoiceId: "b", row: 0, item: "Oven", price: 13695 },
  { invoiceId: "b", row: 1, item: "Oven", price: 12427 },
  { invoiceId: "9b54-dbdd", row: 0, item: "Oven", price: 9830 },
  { invoiceId: "9b54-dbdd", row: 1, item: "Recliner", price: 6244 },
  { invoiceId: "9b54-dbdd", row: 2, item: "Dryer", price: 6946 },
  { invoiceId: "2cac788-", row: 0, item: "Recliner", price: 115 },
  { invoiceId: "2cac788-", row: 1, item: "Dishwasher", price: 1377 },
  { invoiceId: "2cac788-", row: 2, item: "Dryer", price: 6627 },
  { invoiceId: "99cd9c14", row: 0, item: "Recliner", price: 1794 },
  { invoiceId: "99cd9c14", row: 1, item: "Dishwasher", price: 7142 },
  { invoiceId: "99cd9c14", row: 2, item: "Dryer", price: 2253 },
  { invoiceId: "99cd9c14", row: 3, item: "Oven", price: 13509 },
  { invoiceId: "a1854b-14b", row: 0, item: "Refrigerator", price: 3373 },
  { invoiceId: "a1854b-14b", row: 1, item: "Dryer", price: 7821 },
  { invoiceId: "a1854b-14b", row: 2, item: "Oven", price: 12542 },
  { invoiceId: "43b76a75", row: 0, item: "Oven", price: 5569 },
  { invoiceId: "43b76a75", row: 1, item: "Refrigerator", price: 13791 },
  { invoiceId: "43b76a75", row: 2, item: "Dishwasher", price: 6762 },
  { invoiceId: "43b76a75", row: 3, item: "Dishwasher", price: 9957 },
  { invoiceId: "95b971959", row: 0, item: "Dryer", price: 5341 }
];

const request = window.indexedDB.open('database', 1);

// Create database
request.onupgradeneeded = event => {
    const db = event.target.result;
    
    const invoiceStore = db.createObjectStore('invoices', { keyPath: 'invoiceId' });
    invoiceStore.createIndex('VendorIndex', 'vendor');
    invoices.forEach(invoice => invoiceStore.add(invoice));

    const itemStore = db.createObjectStore('invoice-items', { keyPath: ['invoiceId', 'row'] });
    itemStore.createIndex('InvoiceIndex', 'invoiceId');  
    invoiceItems.forEach(invoiceItem => itemStore.add(invoiceItem));
};

request.onsuccess = () => {
    const db = request.result;
    const transaction = db.transaction(['invoices', 'invoice-items'], 'readwrite');
    const invoiceStore = transaction.objectStore('invoices');
    const itemStore = transaction.objectStore('invoice-items');
    const vendorIndex = invoiceStore.index('VendorIndex');
    const invIndex = itemStore.index('InvoiceIndex');
    
    // Get cursor on invoice store simply to print all invoices
    const getCursorRequest = invoiceStore.openCursor();
    getCursorRequest.onsuccess = e => {
        const cursor = e.target.result;
        if (cursor) {
            console.log(cursor.value);
            cursor.continue();
        } else {
            console.log('Exhausted all documents');
        }
    }

    // Get cursor on vendor index of invoice store to update all 'GE' vendors to 'P&GE'
    const keyRng = IDBKeyRange.only('GE');
    const updateCursorRequestIndex = vendorIndex.openCursor(keyRng);
    updateCursorRequestIndex.onsuccess = e => {
        const cursor = e.target.result;
        if (cursor) {
            const invoice = cursor.value;
            invoice.vendor = 'P&GE';
            cursor.update(invoice);

            cursor.continue();
        }
    }

    // Get cursor to delete all Frigidaire invoices
    const deleteInvoiceCursorRequest = vendorIndex.openCursor(IDBKeyRange.only('Frigidaire'));
    deleteInvoiceCursorRequest.onsuccess = e => {
        const invCursor = e.target.result;
        if (invCursor) {
            // Get invoice item cursor
            const invItemCursorRequest = invIndex.openCursor(IDBKeyRange.only(invCursor.value.invoiceId));
            invItemCursorRequest.onsuccess = e => {
                const invItemCursor = e.target.result;
                if (invItemCursor) {
                    invItemCursor.delete();
                    invItemCursor.continue();
                }
            }
            invCursor.delete();
            invCursor.continue();
        }
    }
};