Скачать или смотреть How to Delete Multiple Elements by Properties from an Array in JavaScript

Learn how to effectively filter out multiple elements from an array based on specific properties using JavaScript's built-in methods.
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Deleting Multiple Elements by Properties from an Array in JavaScript

Filtering arrays in JavaScript is a common task developers face when working with data. In this guide, we will explore a specific problem: how to delete multiple elements from an array of objects based on properties from another array. This is a typical scenario you might encounter while managing user data where you need to remove specific entries.

The Problem

Imagine you have an array of objects where each object represents a user, and each user has a userId. You also have an array called bar, which contains userIds that you want to filter out from the first array. Your task is to return a new array without the unwanted userIds.

Here is a quick overview of the data:

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When you filter foo using bar, your expected output is:

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However, you might find that using Array.prototype.filter() with Array.prototype.some() doesn't yield the results you expect when bar has multiple elements.

Understanding the Issue

The issue arises from how you are checking for matching userIds. Your filter condition might look something like this:

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

In this case, you're checking if at least one item in bar is not equal to each userId, which will always be true for all users in foo as long as there's any id in bar that doesn't match it. As a result, this condition does not help you filter out the userIds present in bar.

The Solution

To solve this problem, you need to modify the filter condition so that it checks if a userId exists in bar and returns its inverse value. Here's the corrected code:

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Breaking it Down

Filter Method: This method creates a new array with all elements that pass the test implemented by the provided function.

Some Method: This method tests whether at least one element in the bar array passes the test implemented by the provided function.

Negation: By using ! before bar.some(), we invert the condition. We are effectively asking: "keep this user if their userId is NOT found in the bar array."

Complete Example

Here’s how the complete code looks after modification:

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Expected Output

When you run the above code, the output will correctly exclude the unwanted userIds:

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

Conclusion

In conclusion, filtering an array of objects by some conditions can sometimes be tricky, especially when dealing with multiple matching criteria. By understanding the workings of Array.prototype.filter() and Array.prototype.some(), we can effectively manage our data.

Now, whenever you encounter the need to filter elements based on properties from arrays, you can apply this method confidently!