How to use Recursive Types In Typescript
Recursive types in TypeScript allow types to reference themselves within their own definition. By recursively traversing nested arrays, we can build a union type that captures all possible values.
Syntax:
type UnionFromArray<T extends any[][]> = T extends [infer U, ...infer Rest] ? (U | UnionFromArray<Rest>) : never;
Example: In this example, we define a type UnionFromArray that takes a nested array as input. It recursively traverses the nested arrays, combining the types of their elements into a union.
type UnionFromArray<T extends any[][]> =
T extends [infer U, ...infer Rest]
?
(U | UnionFromArray<Rest>) : never;
const nestedArrays =
[
[1, 2],
['a', 'b'],
[true, false]
];
type UnionType = UnionFromArray<typeof nestedArrays>;
const exampleValue: UnionType =
nestedArrays[2][0];
console.log(exampleValue);
Output:
true
How to Create a Union Type from Nested Array in TypeScript ?
TypeScript developers often encounter scenarios where they need to represent a value that could be one of several different types. TypeScript’s union types provide a solution to this problem by allowing variables to hold values of multiple types. However, when dealing with nested arrays, each nested array might represent a different type, making it challenging to create a union type that encompasses all possible values.
There are several approaches to creating a Union type from nested arrays in TypeScript which are as follows:
Table of Content
- Using Type Assertions
- Using Conditional Types
- Using Recursive Types