What are some common mistakes when using union types in TypeScript?

What are some common mistakes when using union types in TypeScript?

Some common mistakes include not handling all possible types, using overly broad unions, and forgetting to check types at runtime.

Can you give an example of a mistake with union types?

Sure! A common mistake is assuming a variable of a union type is always of a specific type without type narrowing.

How can I avoid these mistakes?

You can avoid these mistakes by using type guards, ensuring exhaustive checks, and leveraging TypeScript's strict mode.

What are type guards?

Type guards are functions or expressions that allow you to narrow down the type of a variable within a conditional block.

Can you show me a code example of a type guard?

Certainly! Here's a simple example:

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

const value: string | number = 'Hello';
if (isString(value)) {
    console.log(value.toUpperCase()); // Safe to call string methods
}