What is Omit?
In TypeScript, the Omit utility type is a convenient tool for creating new types by excluding specific properties from an existing type. It allows you to take an object type and specify which properties you want to remove, effectively creating a new type that lacks those properties. This can be useful when you need to work with variations of data structures or when you want to ensure that certain properties are excluded from a type to meet specific requirements.
type Omit<T, K extends string | number | symbol> = {
[P in Exclude<keyof T, K>]: T[P];
};
How Does Omit Work?
Suppose you have a Product type that includes properties like id, name, price, and category. If you need to create a simplified product type that only requires name and price, you can utilize the Omit utility to exclude id and category from the Product type.
type Product = {
id: number;
name: string;
price: number;
category: string;
};
type SimplifiedProduct = Omit<Product, "id" | "category">;
const simplifiedProduct: SimplifiedProduct = {
name: "Widget",
price: 19.99,
// No "id" and "category" properties allowed here
};
Recap
The Omit utility type is commonly used in situations where you want to create a more refined type definition without duplicating code or manually specifying every property.
You might find this concept resembling one of the utility types called Exclude. While both Exclude and Omit serve the purpose of excluding or omitting specific elements from a set of types, they differ in their applications. Exclude is designed for working with type unions, whereas Omit is specifically used for omitting specific properties from a type.
Resources
TypeScript Utility Types - Exclude
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