TypeScript: remove key from type/subtraction type
Update for TypeScript 3.5: The Omit<Type, Keys>
utility type is now available. Please see Mathias' answer for an example usage.
Old Answer: Since TypeScript 2.8 and the introduction of Exclude
, It's now possible to write this as follows:
type Without<T, K> = { [L in Exclude<keyof T, K>]: T[L]};
Or alternatively, and more concisely, as:
type Without<T, K> = Pick<T, Exclude<keyof T, K>>;
For your usage, you could now write the following:
type ExcludeCart<T> = Without<T, "cart">;
While this has been correctly answered, I wanted to point out that TypeScript 3.5 did add an Omit<T, E>
type.
type NoCart = Omit<{foo: string, bar: string, cart: number}, "cart">;
This results in the {foo: string, bar: string}
type.
While there isn't a built-in subtraction type, you can currently hack it in:
type Sub0< O extends string, D extends string,> = {[K in O]: (Record<D, never> & Record<string, K>)[K]}type Sub< O extends string, D extends string, // issue 16018 Foo extends Sub0<O, D> = Sub0<O, D>> = Foo[O]type Omit< O, D extends string, // issue 16018 Foo extends Sub0<keyof O, D> = Sub0<keyof O, D>> = Pick<O, Foo[keyof O]>
In the question's case, you would do:
type ExcludeCart<T> = Omit<T, 'cart'>
With TypeScript >= 2.6, you can simplify it to:
/** * for literal unions * @example Sub<'Y' | 'X', 'X'> // === 'Y' */export type Sub< O extends string, D extends string > = {[K in O]: (Record<D, never> & Record<string, K>)[K]}[O]/** * Remove the keys represented by the string union type D from the object type O. * * @example Omit<{a: number, b: string}, 'a'> // === {b: string} * @example Omit<{a: number, b: string}, keyof {a: number}> // === {b: string} */export type Omit<O, D extends string> = Pick<O, Sub<keyof O, D>>