What are decorators in TypeScript and can you give me some examples?

What are decorators in TypeScript and can you give me some examples?

Decorators in TypeScript are special annotations that can be attached to classes, methods, or properties. They allow you to modify the behavior of the target they are applied to. For example, you can use decorators to log method calls, validate inputs, or even modify class properties.

Can you show me a simple example of a method decorator?

Sure! Here's a simple method decorator that logs the method name and its arguments:

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

How would I use this decorator in a class?

You can use the @LogMethod decorator above a method in your class like this:

class Example {
    @LogMethod
    greet(name: string) {
        return `Hello, ${name}!`;
    }
}

What happens when I call the greet method?

When you call the greet method, it will log the method name and the arguments to the console before executing the original method. For example, calling new Example().greet('Alice') will log Calling greet with arguments: Alice.