What are the best practices for using type guards in TypeScript?

What are the best practices for using type guards in TypeScript?

Type guards are essential for ensuring type safety in TypeScript. Best practices include using the typeof operator for primitive types, creating user-defined type guards for complex types, and leveraging the instanceof operator for class instances.

Can you give an example of a user-defined type guard?

Sure! A user-defined type guard can be a function that checks if an object is of a specific type. For example:

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

This function can be used to narrow down types in conditional statements.

What about using type guards with union types?

When working with union types, type guards help you determine which type you're dealing with. For instance:

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

This ensures that you handle each type appropriately.

Are there any performance considerations with type guards?

Yes, while type guards are powerful, excessive or complex type checks can impact performance. It's best to use them judiciously and avoid deep nesting of type checks.