Скачать или смотреть Understanding VueJS Filtering: Why Your Array Changes and How to Fix It

Discover how to effectively filter arrays in VueJS without modifying the original data. Learn the importance of array references and solutions to common filtering issues.
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Understanding VueJS Filtering: Why Your Array Changes and How to Fix It

Filtering arrays in JavaScript, particularly within the VueJS framework, is a common requirement when dealing with multiple datasets. However, it's easy to encounter some pitfalls along the way — especially when you notice unexpected changes to your original array. This guide will break down a common issue related to filtering arrays in VueJS and will provide a clear solution to ensure your data integrity remains intact.

The Problem: Array Filtering Gone Wrong

You might find yourself in a situation where you are trying to filter an array based on the contents of another array, but you notice that the original array (this.unfilteredArray) is being modified when you perform the filtering. This can lead to frustrating scenarios where you only see a part of your expected results. Let’s look at a specific example where this problem manifests.

Your Code Setup

In this scenario, you have two arrays:

this.unfilteredArray: Contains a list of values, e.g., ["1", "2", "4", "3"]

this.filteredNumbers: Contains the numbers you want to filter on, e.g., ["2"]

Here’s your initial function for filtering the array:

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

The intention is to filter this.unfilteredArray based on the contents of this.filteredNumbers, however, if you add more numbers to this.filteredNumbers, you notice that this.unfilteredArray seems to lose its initial values. Why is that happening?

The Explanation: Understanding Array References

The crux of the issue lies in how JavaScript handles array assignment. When you write:

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

You are not creating a new array; instead, you are merely creating a reference to this.unfilteredArray. Thus, any modifications to filteredArray will reflect on this.unfilteredArray because they point to the same data structure.

How Filtering Affects the Original Array

When you do the following operation:

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

The variable filteredArray is now ensured to contain filtered results, but since it references this.unfilteredArray, it has now affected the original data when you reassigned it.

The Solution: Returning a Properly Filtered Array

The simple way to avoid this behavior is to return a new filtered array without referencing the original. Here’s how you can do it correctly:

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

With this approach, you're ensuring that each call to filteredArray evaluates this.unfilteredArray independently, preserving its original state and data.

Reassurance of Data Integrity

By using this method, you can filter your arrays effectively without compromising the integrity of your original data. This is crucial for maintaining consistency in larger applications where multiple components may rely on the same data sets.

Handling Multiple Arrays: Filtering Object Properties

If your requirements expand to filtering multiple arrays contained within an object, a similar approach should be taken. You would create separate filter operations for each array within the object. Here’s a conceptual implementation:

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

Key Points to Remember

Avoid Modifying Original Arrays: Always return a new array instead of assigning the filtered result to a variable that references the original.

Maintain Data Structure: When filtering multiple arrays in an object, ensure to preserve the structure while updating the relevant parts only.

Conclusion

The key takeaway here is that when filtering arrays in VueJS, it is vital to create new arrays to avoid inadvertently altering your original data