Adding and reading data

Learn to add and get data through a transaction.

What is a transaction?

Every read and write in IndexedDB happens inside a transaction. You start one with db.transaction(storeName, mode). The mode is either 'readonly' or 'readwrite'.

const tx = db.transaction('notes', 'readwrite');

A transaction gives the store a consistent scope; on error, all changes are rolled back. When the work is done, the transaction closes automatically.

Adding and reading data

From the transaction, you get the store with objectStore('notes'), then add a new record with store.add(obj). To read a record, use store.get(key).

const store = tx.objectStore('notes');
store.add({ id: 1, text: 'Hello' });

Both calls return an IDBRequest; you read the result with request.onsuccess. Calling add with an existing key throws; use put to overwrite.

Exercise Add a note through a transaction

Open a 'readwrite' transaction on the 'notes' store with db.transaction and assign it to tx. Get the store with tx.objectStore('notes') into a store variable. Call store.add with the object { id: 1, text: 'Hello' }.

Show example solution

const tx = db.transaction('notes', 'readwrite');
const store = tx.objectStore('notes');
store.add({ id: 1, text: 'Hello' });

Test yourself

Match transaction parts

'readonly'

read only
'readwrite'

read and write
objectStore()

get the store
transaction()

start operation

Add a new record to the store

store.____({ id: 1, text: 'Hello' });

Show answer

store.add({ id: 1, text: 'Hello' });

Which mode is used to add data?
- 'readonly'
- 'readwrite'
- 'writeonly'
- 'add'
Show answer

'readwrite' — Correct! Inside a 'readwrite' transaction you can call add and put.

Next lesson: Indexes and queries

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