Very Simple IndexedDB Example

IndexedDB101.js

// This works on all devices/browsers, and uses IndexedDBShim as a final fallback 
var indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB || window.shimIndexedDB;

// Open (or create) the database
var open = indexedDB.open("MyDatabase", 1);

// Create the schema
open.onupgradeneeded = function() {
    var db = open.result;
    var store = db.createObjectStore("MyObjectStore", {keyPath: "id"});
    var index = store.createIndex("NameIndex", ["name.last", "name.first"]);
};

open.onsuccess = function() {
    // Start a new transaction
    var db = open.result;
    var tx = db.transaction("MyObjectStore", "readwrite");
    var store = tx.objectStore("MyObjectStore");
    var index = store.index("NameIndex");

    // Add some data
    store.put({id: 12345, name: {first: "John", last: "Doe"}, age: 42});
    store.put({id: 67890, name: {first: "Bob", last: "Smith"}, age: 35});
    
    // Query the data
    var getJohn = store.get(12345);
    var getBob = index.get(["Smith", "Bob"]);

    getJohn.onsuccess = function() {
        console.log(getJohn.result.name.first);  // => "John"
    };

    getBob.onsuccess = function() {
        console.log(getBob.result.name.first);   // => "Bob"
    };

    // Close the db when the transaction is done
    tx.oncomplete = function() {
        db.close();
    };
}

I have a comment, which is more of a question. You execute four operations against the store (two writes and two reads). The database is closed when the transaction is completed. From what I there is a high risk that the database will be closed before one of the operations is actually completed. Am I right or am I missing something?

This one could answer your question:
https://stackoverflow.com/questions/34915581/indexeddb-when-to-close-a-connection

Thanks