What is indexedDB

The lightweight promised based wrapper for indexedDB

What is indexedDB?

IndexedDB is a large-scale, NoSQL storage system. It lets you store just about anything in the user's browser. In addition to the usual search, get, and put actions, IndexedDB also supports transactions.

Here is the definition of IndexedDB on MDN:

"IndexedDB is a low-level API for client-side storage of significant amounts of structured data, including files/blobs. This API uses indexes to enable high performance searches of this data. While DOM Storage is useful for storing smaller amounts of data, it is less useful for storing larger amounts of structured data. IndexedDB provides a solution."

Each IndexedDB database is unique to an origin (typically, this is the site domain or subdomain), meaning it cannot access or be accessed by any other origin. Data storage limits are usually quite large, if they exist at all, but different browsers handle limits and data eviction differently.

IndexedDB terms

Database - This is the highest level of IndexedDB. It contains the object stores, which in turn contain the data you would like to persist. You can create multiple databases with whatever names you choose, but generally there is one database per app. If your are from the SQL world then it our good old DATABASE.

Object store - An object store is an individual bucket to store data. You can think of object stores as being similar to tables in traditional relational databases. Typically, there is one object store for each 'type' (not JavaScript data type) of data you are storing. For example, given an app that persists blog posts and user profiles, you could imagine two object stores. Unlike tables in traditional databases, the actual JavaScript data types of data within the store do not need to be consistent (for example, if there are three people in the 'people' object store, their age properties could be 53, 'twenty-five', and unknown ).

Index- An Index is a kind of object store for organizing data in another object store (called the reference object store) by an individual property of the data. The index is used to retrieve records in the object store by this property. For example, if you're storing people, you may want to fetch them later by their name, age, or favorite animal.

Transaction - A transaction is wrapper around an operation, or group of operations, that ensures database integrity. If one of the actions within a transaction fail, none of them are applied and the database returns to the state it was in before the transaction began. All read or write operations in IndexedDB must be part of a transaction. This allows for atomic read-modify-write operations without worrying about other threads acting on the database at the same time.

Cursor - A mechanism for iterating over multiple records in database.