Typeseedcordv0.10.6

And

Returns a boolean for whether two given types are both truetrue.

Use-case: Constructing complex conditional types where multiple conditions must be satisfied.

See also:AndAll, Or, Xor

type And<
    A extends boolean,
    B extends boolean
> = AndAll<[A, B]>;

type And<
    A extends boolean,
    B extends boolean
> = AndAll<[A, B]>;

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

type TT = And<true, true>;
//=> true

type TF = And<true, false>;
//=> false

type FT = And<false, true>;
//=> false

type FF = And<false, false>;
//=> false

Note: When boolean is passed as an argument, it is distributed into separate cases, and the final result is a union of those cases. For example, And<true, boolean> expands to And<true, true> | And<true, false>, which simplifies to true | false (i.e., boolean).

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

type TT = And<true, true>;
//=> true

type TF = And<true, false>;
//=> false

type FT = And<false, true>;
//=> false

type FF = And<false, false>;
//=> false

Note: When boolean is passed as an argument, it is distributed into separate cases, and the final result is a union of those cases. For example, And<true, boolean> expands to And<true, true> | And<true, false>, which simplifies to true | false (i.e., boolean).

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

type A = And<true, boolean>;
//=> boolean

type B = And<boolean, true>;
//=> boolean

type C = And<false, boolean>;
//=> false

type D = And<boolean, false>;
//=> false

type E = And<boolean, boolean>;
//=> boolean

Note: If either of the types is never, the result becomes false.

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

type A = And<true, boolean>;
//=> boolean

type B = And<boolean, true>;
//=> boolean

type C = And<false, boolean>;
//=> false

type D = And<boolean, false>;
//=> false

type E = And<boolean, boolean>;
//=> boolean

Note: If either of the types is never, the result becomes false.

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

type A = And<true, never>;
//=> false

type B = And<never, true>;
//=> false

type C = And<false, never>;
//=> false

type D = And<never, false>;
//=> false

type E = And<boolean, never>;
//=> false

type F = And<never, boolean>;
//=> false

type G = And<never, never>;
//=> false

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

type A = And<true, never>;
//=> false

type B = And<never, true>;
//=> false

type C = And<false, never>;
//=> false

type D = And<never, false>;
//=> false

type E = And<boolean, never>;
//=> false

type F = And<never, boolean>;
//=> false

type G = And<never, never>;
//=> false

A

A extends boolean

A extends boolean

B

B extends boolean

B extends boolean

import type {And} from 'type-fest'; type TT = And<true, true>; //=> true type TF = And<true, false>; //=> false type FT = And<false, true>; //=> false type FF = And<false, false>; //=> false Note: When boolean is passed as an argument, it is distributed into separate cases, and the final result is a union of those cases. For example, And<true, boolean> expands to And<true, true> | And<true, false>, which simplifies to true | false (i.e., boolean).

import type {And} from 'type-fest'; type A = And<true, boolean>; //=> boolean type B = And<boolean, true>; //=> boolean type C = And<false, boolean>; //=> false type D = And<boolean, false>; //=> false type E = And<boolean, boolean>; //=> boolean Note: If either of the types is never, the result becomes false.

import type {And} from 'type-fest'; type A = And<true, never>; //=> false type B = And<never, true>; //=> false type C = And<false, never>; //=> false type D = And<never, false>; //=> false type E = And<boolean, never>; //=> false type F = And<never, boolean>; //=> false type G = And<never, never>; //=> false