Скачать или смотреть How to Remove Properties from an Object Type in Typescript by Value

Learn how to filter object properties in Typescript using mapped types by removing properties based on their value using an organized, step-by-step guide.
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How to Remove Properties from an Object Type in Typescript by Value

In the world of TypeScript, developers often encounter scenarios where they need to manipulate object types dynamically. One such scenario may involve removing properties from an object type based on their values rather than their keys. This can be particularly useful for ensuring your types are tidy and contain only the relevant data you need for your application.



The Challenge: Removing Properties Based on Value

Consider we have the following TypeScript type:

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

In this structure, we want to "filter" out the property b because its type is never. We need a way to create a type that results in only keeping a when b is never.

This opens up the question: Is there a way to remove some properties of an object via a mapped type based on their value?



The Solution: Creating a Helper Type

After exploring different approaches, we identified a powerful solution using a mapped type in TypeScript. This method allows us to specify conditions for the properties we want to keep or discard based on their values.

Step-by-Step Implementation

Define the Helper Type:

We can define a helper type called RemovePropsByValue that will take two type parameters:

T: The original type from which we want to filter properties.

V: The value that we want to use as a criterion for removal.

Here’s how the implementation will look:

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

Usage of the Helper Type:

After defining the helper type, we can apply it to our previous example of type Q:

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

In the example above:

FilteredQ is the resulting type after filtering.

We removed the property b as we specified never as the value.



Benefits of Using Mapped Types

Using mapped types to dynamically filter properties based on their values has several advantages:

Type Safety: Ensures that you end up with types that accurately reflect the properties that matter for your functionalities.

Maintainability: Reduces clutter in your types by removing unnecessary properties, making your code easier to maintain.

Flexibility: This method can be applied to various object types and can handle different value types beyond just never.



Conclusion

By employing mapped types in TypeScript, you can effectively and efficiently remove properties from an object type based on their values. This technique enhances type manipulation and helps maintain cleaner and more intelligible code.

Next time you need to filter properties by value, remember to utilize the RemovePropsByValue helper type to streamline your TypeScript codebase!