Writable<BaseType, Keys>

Writable<BaseType, Keys> = BaseType extends ReadonlyMap<infer KeyType, infer ValueType> ? Map<KeyType, ValueType> : BaseType extends ReadonlySet<infer ItemType> ? Set<ItemType> : BaseType extends readonly unknown[] ? WritableArray<BaseType> : Simplify<Except<BaseType, Keys> & { -readonly [KeyType in keyof Pick<BaseType, Keys>]: Pick<BaseType, Keys>[KeyType] }>

Defined in: packages/react-querybuilder/src/types/type-fest/writable.ts:54

Create a type that strips readonly from the given type. Inverse of Readonly<T>.

The 2nd argument will be ignored if the input type is not an object.

Note: This type can make readonly Set and Map writable. This behavior is different from Readonly<T> (as of TypeScript 5.2.2). See: https://github.com/microsoft/TypeScript/issues/29655

This can be used to store and mutate options within a class, edit readonly objects within tests, construct a readonly object within a function, or to define a single model where the only thing that changes is whether or not some of the keys are writable.

Type Parameters

Type Parameter	Default type
BaseType	-
Keys extends keyof BaseType	keyof BaseType

Example

import type {Writable} from 'type-fest';

type Foo = {
	readonly a: number;
	readonly b: readonly string[]; // To show that only the mutability status of the properties, not their values, are affected.
	readonly c: boolean;
};

const writableFoo: Writable<Foo> = {a: 1, b: ['2'], c: true};
writableFoo.a = 3;
writableFoo.b[0] = 'new value'; // Will still fail as the value of property "b" is still a readonly type.
writableFoo.b = ['something']; // Will work as the "b" property itself is no longer readonly.

type SomeWritable = Writable<Foo, 'b' | 'c'>;
// type SomeWritable = {
// 	readonly a: number;
// 	b: readonly string[]; // It's now writable. The type of the property remains unaffected.
// 	c: boolean; // It's now writable.
// }

// Also supports array
const readonlyArray: readonly number[] = [1, 2, 3];
readonlyArray.push(4); // Will fail as the array itself is readonly.
const writableArray: Writable<typeof readonlyArray> = readonlyArray as Writable<typeof readonlyArray>;
writableArray.push(4); // Will work as the array itself is now writable.

---

caution

API documentation is generated from the latest commit on the main branch. It may be somewhat inconsistent with official releases of React Query Builder.