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. For instance, you can create a logging decorator to track method calls or an authorization decorator to restrict access to certain methods based on user roles.

Can you give me an example of a logging decorator?

Sure! Here's a simple logging decorator:

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

You can use this decorator on any method to log its calls.

How about an example of an authorization decorator?

Absolutely! Here's a basic authorization decorator:

function Authorize(role: string) {
    return function(target: any, propertyName: string, descriptor: PropertyDescriptor) {
        const originalMethod = descriptor.value;
        descriptor.value = function(...args: any[]) {
            if (this.userRole !== role) {
                throw new Error('Unauthorized');
            }
            return originalMethod.apply(this, args);
        };
    };
}

This decorator checks if the user has the required role before executing the method.

What other use cases are there for decorators?

Other use cases include property validation, method timing, and caching results. You can create decorators to enforce validation rules on class properties or to measure the execution time of methods.