Understanding Weird Vue.js Props Behavior with Arrays

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The Problem

For instance, in the beforeMount() lifecycle hook, the properties are copied like so:

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

However, you notice a peculiar behavior: when you edit the other variables and reopen the component, everything resets except for the array. This can be puzzling because you've made sure not to interact directly with the props throughout your code, yet the array remains unaffected by the resets.

Why Does This Happen?

The core of the problem lies in how JavaScript handles objects and arrays. When you assign an array (or an object) to another variable in JavaScript, you're not creating a new independent copy. Instead, you're passing a reference to the same array in memory. Thus, any changes made to the array in the local component will also reflect on the original prop.

Key Points:

Reference vs. Value: Objects and arrays in JavaScript are reference types. Directly assigning them doesn’t create a new instance; it only points to the existing one.

The Effective Solution

To create a separate copy of the array and avoid those unexpected resets, you can utilize the spread operator to clone the array. Here’s how you can achieve it:

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

Explanation of the Solution:

Additional Considerations

Use v-if carefully: While v-if can control component rendering, its effectiveness may vary depending on how you manage state and props.

Component Keys: Ensure that you are correctly leveraging component keys if you are trying to force remounts; this often helps in resetting the component state.

Watchers: You can also consider using Vue's watchers to reactively update variables based on prop changes if needed.

Conclusion