Type Alias Spread<FirstType, SecondType>

Spread: FirstType extends TupleOrArray
    ? SecondType extends TupleOrArray
        ? SpreadTupleOrArray<FirstType, SecondType>
        : Simplify<SpreadObject<FirstType, SecondType>>
    : Simplify<SpreadObject<FirstType, SecondType>>

Mimic the type inferred by TypeScript when merging two objects or two arrays/tuples using the spread syntax.

Type Parameters

  • FirstType extends Spreadable
  • SecondType extends Spreadable

Example

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

type Foo = {
	a: number;
	b?: string;
};

type Bar = {
	b?: number;
	c: boolean;
};

const foo = {a: 1, b: '2'};
const bar = {c: false};
const fooBar = {...foo, ...bar};

type FooBar = Spread<Foo, Bar>;
// type FooBar = {
// 	a: number;
// 	b?: string | number | undefined;
// 	c: boolean;
// }

const baz = (argument: FooBar) => {
	// Do something
}

baz(fooBar);

Example

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

const foo = [1, 2, 3];
const bar = ['4', '5', '6'];

const fooBar = [...foo, ...bar];
type FooBar = Spread<typeof foo, typeof bar>;
// FooBar = (string | number)[]

const baz = (argument: FooBar) => {
	// Do something
};

baz(fooBar);

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