What are some examples of type guards in TypeScript?

What are some examples of type guards in TypeScript?

Type guards are techniques used to narrow down the type of a variable. For example, you can use the typeof operator.

Can you show me a specific example using typeof?

Sure! Here's an example:

function example(value: number | string) {
    if (typeof value === 'string') {
        console.log('String:', value);
    } else {
        console.log('Number:', value);
    }
}

This function checks if value is a string or a number.

What about using instanceof for class instances?

Great question! You can use instanceof to check if an object is an instance of a specific class. For example:

class Dog {
    bark() { console.log('Woof!'); }
}

function makeSound(animal: Dog | string) {
    if (animal instanceof Dog) {
        animal.bark();
    } else {
        console.log('Animal sound: ' + animal);
    }
}