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home / developersection / interviews / how do you handle version changes in indexeddb?
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Ponu Maurya
Ponu Maurya

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Ponu Maurya
Ponu Maurya 03 Jul 2025
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Handling version changes in IndexedDB is a critical part of managing schema upgrades (like adding new object stores or indexes).

How Versioning Works in IndexedDB

Every IndexedDB database has a version number (default is 1). A version change triggers the onupgradeneeded event. You can only modify the database structure (create/delete object stores, indexes, etc.) inside this event.

Version Change Flow

const request = indexedDB.open("MyDatabase", 2); // Version 2 triggers upgrade

request.onupgradeneeded = function (event) {
    const db = event.target.result;
    const oldVersion = event.oldVersion;
    const newVersion = event.newVersion;
    console.log(`Upgrading from version ${oldVersion} to ${newVersion}`);

    if (oldVersion < 1) {
        const store = db.createObjectStore("users", { keyPath: "id" });
        store.createIndex("name", "name", { unique: false });
    }

    if (oldVersion < 2) {
        const store = db.transaction.objectStore("users");
        store.createIndex("email", "email", { unique: true });
    }
};

request.onsuccess = function (event) {
    const db = event.target.result;
    console.log("Database opened successfully.");
};

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

Key Points

Feature Explanation
indexedDB.open(name, version) Pass a higher version number to trigger schema changes.
onupgradeneeded Only place you can create/remove object stores and indexes.
event.oldVersion The version you’re upgrading from.
event.newVersion The version you’re upgrading to.
Safe Upgrades Always use version checks like if (oldVersion < x) to support multi-step upgrades.

Best Practice

  • Always increment the version number when changing schema.
  • Never use put/add/delete inside onupgradeneeded unless necessary — structure only.
  • Use feature flags or version guards to keep upgrades backward-compatible.
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