Seamless Digital Experience.
Happy Customers.

Digital Experience and Error Monitoring Platform - Zipy

Mastering Svelte Store Errors: A Comprehensive Guide to Debugging and Fixing

Vishalini Paliwal
~ 4 min read | Published on Feb 28, 2024


Fix bugs faster with Zipy!

  • Session replay
  • Network calls
  • Console Logs
  • Stack traces
  • User identification
Get Started for Free


Welcome to our deep dive into Debugging Store Errors in Svelte. If you've encountered pesky store errors while working with Svelte, you're not alone. These errors can disrupt your workflow and slow down project progress. However, with the right knowledge and tools, you can efficiently handle and fix these errors. This article will guide you through understanding and solving common Svelte store errors, ensuring your development process is smoother and more efficient.

Catch errors proactively with Zipy. Sign up for free!

Try Zipy now

Understanding Store Errors in Svelte

Svelte stores are a powerful feature for managing app state reactively. However, errors can arise due to various reasons like improper store subscriptions, mutations outside of store methods, or issues with store updates. Recognizing and fixing these errors is crucial for maintaining the integrity of your application's state management.

Scenario 1

Error Code

import { writable } from 'svelte/store';

const counter = writable(0);

counter = counter + 1; // Attempt to mutate store value directly

Corrected Code

import { writable } from 'svelte/store';

const counter = writable(0);

counter.update(n => n + 1); // Correctly updates the store value

Solution Summary

The error was caused by trying to mutate the store value directly. In Svelte, store values should be updated using the update or set methods provided by the store.

Scenario 2

Error Code

import { writable } from 'svelte/store';

const userProfile = writable({ name: 'Alex', age: 30 }); = 'Sam'; // Attempt to mutate a store's property directly

Corrected Code

import { writable } from 'svelte/store';

const userProfile = writable({ name: 'Alex', age: 30 });

userProfile.update(profile => ({ ...profile, name: 'Sam' })); // Corrects the mutation method

Solution Summary

This error occurred due to direct mutation of a store's property. The correct approach is to use the update method with a function that returns a new object, incorporating the changes.

Scenario 3

Error Code

import { writable } from 'svelte/store';

let count = writable(0);

$: doubled = count * 2; // Incorrectly referencing store value

Corrected Code

import { writable } from 'svelte/store';

let count = writable(0);

$: doubled = $count * 2; // Correctly references the store value

Solution Summary

The error was a result of not using the store value correctly within a reactive statement. In Svelte, you should use the $ prefix to refer to store values reactively.

Handling Store Errors in Svelte

To effectively handle store errors in Svelte, always ensure to use store methods (set, update) for mutations, use the $ syntax for reactive values, and thoroughly test store logic to catch errors early.

Proactive Error Debugging with Zipy

To further enhance your debugging capabilities, consider using Zipy for proactive error monitoring and user session replay. Zipy's tools allow you to catch runtime errors in Svelte, offering insights and playback features to understand and resolve issues quickly.

Debug and fix code errors with Zipy Error Monitoring.

Sign up for free


Understanding and fixing Svelte Store Errors is crucial for any developer looking to create seamless, reactive applications. With the strategies and examples provided, you'll be better equipped to manage and debug these errors, enhancing your Svelte development experience.

Resources on how to debug and fix Svelte errors

Frequently Asked Questions

What is a Svelte store?

Svelte stores are constructs provided by Svelte for managing application state reactively. They help in keeping the app's state in sync across components.

How do I update a Svelte store correctly?

To update a Svelte store, use the set or update methods provided by the store. Avoid direct mutations to the store's value.

Can I use async functions with Svelte stores?

Yes, you can use async functions to update Svelte stores by either using the async keyword with the update method or resolving promises within store updates.

Why am I seeing undefined when accessing a store value?

This usually happens if you forget to use the $ syntax to subscribe to a store value in your component. Ensure you're using $storeName to access the store's value reactively.

How can Zipy help with Svelte store errors?

Zipy provides proactive error monitoring and session replay capabilities, allowing developers to catch and debug runtime Svelte store errors more efficiently.

Key Takeaways

  • Correctly update stores using set and update methods to avoid direct mutation errors.
  • Use the$ syntax for reactive subscriptions to store values within components.
  • Test store logic thoroughly to catch and fix errors early in the development process.
  • Leverage tools like Zipy for proactive error monitoring and debugging support, enhancing your ability to handle Svelte store errors effectively.

Call to Action

Feel free to comment or write to us in case you have any further questions at We would be happy to help you. In case you want to explore for your app, you can sign up or book a demo.

Fix bugs faster with Zipy!

Get Started for Free
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

Want to solve customer bugs even before they're reported?

The unified digital experience platform to drive growth with Product Analytics, Error Tracking, and Session Replay in one.

SOC 2 Type 2
Zipy is GDPR and SOC2 Type II Compliant
© 2023 Zipy Inc. | All rights reserved
by folks just like you
// open links in new tab script