More about Conditional Types

1. Syntax of Conditional Types

The syntax for a conditional type is:

T extends U ? X : Y

• T: The type to evaluate.
• U: The condition to check (T extends U).
• X: The type returned if the condition is true.
• Y: The type returned if the condition is false.

2. Example: Basic Conditional Type

The following example checks if a type T is a string:

type IsString<T> = T extends string ? true : false;

type Test1 = IsString<string>; // true
type Test2 = IsString<number>; // false

Here, Test1 resolves to true because string extends string, while Test2 resolves to false because number does not extend string.