What are some practical use cases for decorators in TypeScript?

What are some practical use cases for decorators in TypeScript?

Decorators in TypeScript can be used for various purposes, such as logging, access control, and validation.

Can you give me an example of a logging decorator?

Sure! A logging decorator can be used to log method calls. For example:

function Log(target: any, propertyName: string, descriptor: PropertyDescriptor) {
    const originalMethod = descriptor.value;
    descriptor.value = function(...args: any[]) {
        console.log(`Calling ${propertyName} with args: ${JSON.stringify(args)}`);
        return originalMethod.apply(this, args);
    };
}

What about using decorators for validation?

You can create a validation decorator to check if the input meets certain criteria before executing a method. For example:

function Validate(target: any, propertyName: string, descriptor: PropertyDescriptor) {
    const originalMethod = descriptor.value;
    descriptor.value = function(...args: any[]) {
        if (!args[0]) {
            throw new Error('Invalid input!');
        }
        return originalMethod.apply(this, args);
    };
}

Are there any performance implications of using decorators?

Yes, decorators can introduce some overhead, especially if they perform complex operations. It's important to use them judiciously.