What are the different types of decorators in TypeScript?

What are the different types of decorators in TypeScript?

In TypeScript, decorators are special declarations that can be attached to classes, methods, properties, or parameters. There are four main types of decorators: class decorators, method decorators, accessor decorators, and parameter decorators.

Can you explain each type of decorator?

Sure!

1. Class Decorators: These are applied to a class and can modify its behavior or properties.
2. Method Decorators: These are used on methods to modify their behavior.
3. Accessor Decorators: These are similar to method decorators but are used on getters and setters.
4. Parameter Decorators: These are used to modify the parameters of a method.

Can you give an example of a class decorator?

Absolutely! Here's a simple example of a class decorator:

function LogClass(target: Function) {
    console.log(`Class ${target.name} is created.`);
}

@LogClass
class MyClass {
    constructor() {
        console.log('MyClass instance created.');
    }
}

This decorator logs a message when the class is created.

What about method decorators?

Method decorators can be used to log method calls or modify their behavior. Here's an example:

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);
    };
}

class MyClass {
    @LogMethod
    myMethod(arg: string) {
        console.log(`Method called with argument: ${arg}`);
    }
}

This decorator logs the arguments passed to the method.