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Learn how to effectively track changes in Vue.js computed properties and implement a watcher that responds after initialization.
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This video is based on the question https://stackoverflow.com/q/62941902/ asked by the user 'MartynW' ( https://stackoverflow.com/u/6599698/ ) and on the answer https://stackoverflow.com/a/62941978/ provided by the user 'yooneskh' ( https://stackoverflow.com/u/5202815/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Track Deep Changes in a Computed Object with Vue.js Watcher

Vue.js is a powerful JavaScript framework that allows developers to build interactive user interfaces with ease. However, sometimes, we encounter challenges when managing data changes—especially in complex scenarios involving computed properties and watchers. In this post, we are tackling a common issue: how to track deep changes in a computed object within a Vue component while ensuring that specific actions occur only after the component has fully initialized.

The Problem: Tracking Changes in Computed Properties

Imagine you have a computed property named schedule that fetches the schedule object based on some criteria (like a user-selected name). You also want to watch for any changes in this schedule object to trigger updates to your component's appearance—such as changing a color.

Here's the setup you might have:

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The issue arises because the schedule object is re-evaluated when the component loads, causing your color change to happen immediately, rather than after you've manipulated the properties.

The Solution: Using a Flag to Control Changes

To achieve the desired functionality, you can implement a simple flag in your component's data that will help you control when to change the color based on changes to the schedule object. Here’s a step-by-step guide on how to do it:

Step 1: Add a Flag to Your Data

Start by adding a flag to your component's data. This flag will help determine if your component is in an initialized state or not.

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Step 2: Modify the Watcher

Next, modify your watcher to check if the scheduleInitialized flag is set before changing the color:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Set the Flag After Initialization

Once your component has finished loading, set the scheduleInitialized flag to true. You can do this in the mounted lifecycle hook:

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Final Implementation

Putting it all together, your component will now look something like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

With this simple addition of a flag and a few modifications to your watcher, you can efficiently manage when to apply changes based on the schedule computed property. This approach ensures that your color change happens only after you have manually changed the object's properties, enhancing the user experience in your Vue.js application.

Feel free to reach out if you have further questions or need more assistance with Vue.js! Happy coding!