What are TypeScript type guards and how do they work?

What are TypeScript type guards and how do they work?

TypeScript type guards are techniques used to narrow down the type of a variable within a conditional block. They help ensure type safety.

Can you give me an example of a type guard?

Sure! A common type guard is the typeof operator. For instance:

function isString(value: any): value is string {
    return typeof value === 'string';
}

This function checks if a value is a string.

Are there other types of type guards?

Yes, there are several types, including user-defined type guards, instanceof, and discriminated unions. Each serves different use cases.

How do I use a user-defined type guard?

You can create a user-defined type guard by defining a function that returns a type predicate. For example:

function isCat(animal: Animal): animal is Cat {
    return animal.type === 'cat';
}