Get Set Del Can Throw Sync And Do Not Always Return A Promise

Introduction

IndexedDB is a powerful client-side storage system that allows web applications to store large amounts of data locally within a user's browser. It provides a way to store data in a structured format, making it easier to manage and retrieve data. However, IndexedDB has some quirks that can lead to unexpected behavior, especially when it comes to its methods. In this article, we will explore the issue of get, set, delete, clear, and transaction methods throwing sync and not always returning a promise.

Understanding IndexedDB Methods

IndexedDB provides several methods for interacting with the database, including get, set, delete, clear, and transaction. These methods are used to retrieve, update, delete, and clear data from the database, as well as to execute transactions that involve multiple operations. However, as we will see, these methods can throw sync and do not always return a promise.

Get Method Can Throw Sync

The get method is used to retrieve data from the database. It takes a key or a key range as an argument and returns a promise that resolves to the retrieved data. However, as we will see, the get method can throw sync, which means that it can throw an error immediately, without waiting for the promise to resolve.

console.log('Start')

// Simulate browser not supporting indexed db
delete globalThis.indexedDB

// Should not throw sync
get('any').catch(() => {
 console.log('Error')
})

console.log('End')

In the above code, we simulate a browser that does not support IndexedDB by deleting the indexedDB property from the global object. We then call the get method with the key 'any' and catch any errors that may occur. However, as we can see, the get method throws sync, which means that it throws an error immediately, without waiting for the promise to resolve.

Set Method Can Throw Sync

The set method is used to update data in the database. It takes a key and a value as arguments and returns a promise that resolves to the updated data. However, as we will see, the set method can also throw sync.

console.log('Start')

// Simulate browser not supporting indexed db
delete globalThis.indexedDB

// Should not throw sync
set('any', 'value').catch(() => {
 console.log('Error')
})

console.log('End')

In the above code, we simulate a browser that does not support IndexedDB by deleting the indexedDB property from the global object. We then call the set method with the key 'any' and the value 'value' and catch any errors that may occur. However, as we can see, the set method throws sync, which means that it throws an error immediately, without waiting for the promise to resolve.

Delete Method Can Throw Sync

The delete method is used to delete data from the database. It takes a key as an argument and returns a promise that resolves to the deleted data. However, as we will see, delete method can also throw sync.

console.log('Start')

// Simulate browser not supporting indexed db
delete globalThis.indexedDB

// Should not throw sync
delete('any').catch(() => {
 console.log('Error')
})

console.log('End')

In the above code, we simulate a browser that does not support IndexedDB by deleting the indexedDB property from the global object. We then call the delete method with the key 'any' and catch any errors that may occur. However, as we can see, the delete method throws sync, which means that it throws an error immediately, without waiting for the promise to resolve.

Clear Method Can Throw Sync

The clear method is used to clear all data from the database. It returns a promise that resolves to the cleared data. However, as we will see, the clear method can also throw sync.

console.log('Start')

// Simulate browser not supporting indexed db
delete globalThis.indexedDB

// Should not throw sync
clear().catch(() => {
 console.log('Error')
})

console.log('End')

In the above code, we simulate a browser that does not support IndexedDB by deleting the indexedDB property from the global object. We then call the clear method and catch any errors that may occur. However, as we can see, the clear method throws sync, which means that it throws an error immediately, without waiting for the promise to resolve.

Transaction Method Can Throw Sync

The transaction method is used to execute a transaction that involves multiple operations. It takes a callback function as an argument and returns a promise that resolves to the result of the transaction. However, as we will see, the transaction method can also throw sync.

console.log('Start')

// Simulate browser not supporting indexed db
delete globalThis.indexedDB

// Should not throw sync
transaction('readwrite', () => {
  console.log('Transaction started')
}).catch(() => {
 console.log('Error')
})

console.log('End')

In the above code, we simulate a browser that does not support IndexedDB by deleting the indexedDB property from the global object. We then call the transaction method with the mode 'readwrite' and a callback function that logs a message to the console. However, as we can see, the transaction method throws sync, which means that it throws an error immediately, without waiting for the promise to resolve.

Conclusion

In conclusion, the get, set, delete, clear, and transaction methods of IndexedDB can throw sync and do not always return a promise. This can lead to unexpected behavior and errors in web applications that use IndexedDB. To avoid these issues, developers should always check the return value of these methods and handle any errors that may occur.

Best Practices

To avoid the issues described above, developers should follow these best practices:

• Always check the return value of get, set, delete, clear, and transaction methods.
• Handle any errors that may occur when calling these methods.
• Use try-catch blocks to catch any errors that may occur when calling these methods.
• the async/await syntax to write asynchronous code that is easier to read and maintain.

By following these best practices, developers can avoid the issues described above and write web applications that are more robust and reliable.

Reproduction

The code examples provided in this article can be reproduced in a browser that supports IndexedDB. To reproduce the code examples, follow these steps:

1. Open a browser that supports IndexedDB, such as Google Chrome or Mozilla Firefox.
2. Create a new HTML file and add the following code to it:

<!DOCTYPE html>
<html>
  <head>
    <title>IndexedDB Example</title>
  </head>
  <body>
    <script>
      // Simulate browser not supporting indexed db
      delete globalThis.indexedDB

      // Call get method
      get('any').catch(() => {
        console.log('Error')
      })

      // Call set method
      set('any', 'value').catch(() => {
        console.log('Error')
      })

      // Call delete method
      delete('any').catch(() => {
        console.log('Error')
      })

      // Call clear method
      clear().catch(() => {
        console.log('Error')
      })

      // Call transaction method
      transaction('readwrite', () => {
        console.log('Transaction started')
      }).catch(() => {
        console.log('Error')
      })
    </script>
  </body>
</html>

3. Save the file and open it in the browser.
4. Observe the console output to see the errors that occur when calling the get, set, delete, clear, and transaction methods.

Q: What is IndexedDB?

A: IndexedDB is a client-side storage system that allows web applications to store large amounts of data locally within a user's browser.

Q: What are the methods of IndexedDB?

A: The methods of IndexedDB include get, set, delete, clear, and transaction. These methods are used to retrieve, update, delete, and clear data from the database, as well as to execute transactions that involve multiple operations.

Q: Can the get method throw sync?

A: Yes, the get method can throw sync. This means that it can throw an error immediately, without waiting for the promise to resolve.

Q: Can the set method throw sync?

A: Yes, the set method can also throw sync. This means that it can throw an error immediately, without waiting for the promise to resolve.

Q: Can the delete method throw sync?

A: Yes, the delete method can also throw sync. This means that it can throw an error immediately, without waiting for the promise to resolve.

Q: Can the clear method throw sync?

A: Yes, the clear method can also throw sync. This means that it can throw an error immediately, without waiting for the promise to resolve.

Q: Can the transaction method throw sync?

A: Yes, the transaction method can also throw sync. This means that it can throw an error immediately, without waiting for the promise to resolve.

Q: Why do the IndexedDB methods throw sync?

A: The IndexedDB methods throw sync because they are designed to handle errors immediately, rather than waiting for the promise to resolve. This is because IndexedDB is a client-side storage system, and errors can occur at any time.

Q: How can I avoid the issues caused by the IndexedDB methods throwing sync?

A: To avoid the issues caused by the IndexedDB methods throwing sync, you can use try-catch blocks to catch any errors that may occur when calling these methods. You can also use the async/await syntax to write asynchronous code that is easier to read and maintain.

Q: What are some best practices for using IndexedDB?

A: Some best practices for using IndexedDB include:

• Always check the return value of get, set, delete, clear, and transaction methods.
• Handle any errors that may occur when calling these methods.
• Use try-catch blocks to catch any errors that may occur when calling these methods.
• Use the async/await syntax to write asynchronous code that is easier to read and maintain.

Q: Can I reproduce the code examples provided in this article?

A: Yes, you can reproduce the code examples provided in this article by following these steps:

1. Open a browser that supports IndexedDB, such as Google Chrome or Mozilla Firefox.
2. Create a new HTML file and add the following code it:

<!DOCTYPE html>
<html>
  <head>
    <title>IndexedDB Example</title>
  </head>
  <body>
    <script>
      // Simulate browser not supporting indexed db
      delete globalThis.indexedDB

      // Call get method
      get('any').catch(() => {
        console.log('Error')
      })

      // Call set method
      set('any', 'value').catch(() => {
        console.log('Error')
      })

      // Call delete method
      delete('any').catch(() => {
        console.log('Error')
      })

      // Call clear method
      clear().catch(() => {
        console.log('Error')
      })

      // Call transaction method
      transaction('readwrite', () => {
        console.log('Transaction started')
      }).catch(() => {
        console.log('Error')
      })
    </script>
  </body>
</html>

3. Save the file and open it in the browser.
4. Observe the console output to see the errors that occur when calling the get, set, delete, clear, and transaction methods.

By following these steps, you can reproduce the code examples provided in this article and see the issues described above.