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Home Interviews How do you create and open a database in IndexedDB? – MindStick
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1 Answers

Manish Sharma
Manish Sharma 02 Jul 2025
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To create and open a database in IndexedDB, you use the indexedDB.open() method. This is asynchronous, and you interact with it via event handlers like onsuccess, onerror, and onupgradeneeded.

Basic Steps to Create and Open an IndexedDB Database

Syntax

const request = indexedDB.open(databaseName, version);
  • databaseName: A string, like "MyAppDB"
  • version: A number (e.g., 1) — used to trigger schema upgrades (like adding object stores)

Example: Create and Open a DB

const request = indexedDB.open("MyAppDB", 1);

request.onupgradeneeded = function(event) {
    const db = event.target.result;

    // Create an object store named "users" with "id" as the keyPath
    const store = db.createObjectStore("users", {
        keyPath: "id",
        autoIncrement: true
    });

    // Optional: create an index on "email"
    store.createIndex("emailIndex", "email", { unique: true });

    console.log("Object store and index created.");
};

request.onsuccess = function(event) {
    const db = event.target.result;
    console.log("Database opened successfully", db);
    // Now you can use `db.transaction(...)` to read/write
};

request.onerror = function(event) {
    console.error("Database error:", event.target.error);
};

Summary of Events

Event Purpose
onupgradeneeded Called when DB is created or upgraded (new version)
onsuccess Called when DB is successfully opened
onerror Called if opening DB fails

Tips

  • Use onupgradeneeded to:
    • Create object stores (db.createObjectStore(...))
    • Define indexes
    • Migrate data between versions
  • If the DB already exists with the same version, onupgradeneeded is not triggered.
  • You must perform all schema setup in onupgradeneeded.
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