How to use Conditional Types In Typescript
Conditional types in TypeScript enable developers to create types that depend on other types. By leveraging conditional types, we can dynamically construct a union type based on the values in nested arrays.
Syntax:
type Flatten<T> = T extends Array<infer U> ? U : never;
type UnionFromArray<T extends any[][]> = Flatten<T[number]>;
Example: Here, we define a type UnionFromArray that takes a nested array as input. It flattens the nested array into a single array and then extracts the union of its elements.
type Flatten<T> =
T extends Array<infer U> ? U : never;
type UnionFromArray<T extends any[][]>
= Flatten<T[number]>;
const nestedArrays =
[
[1, 2],
['a', 'b'],
[true, false]
];
type UnionType = UnionFromArray<typeof nestedArrays>;
const exampleValue: UnionType = nestedArrays[1][1];
console.log(exampleValue);
Output
'b'
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