What are some examples of TypeScript decorators?

What are some examples of TypeScript decorators?

TypeScript decorators are special annotations that can be attached to classes, methods, or properties. For example, you can use a class decorator to log when a class is instantiated.

Can you show me a code example of a class decorator?

Sure! Here's a simple class decorator:

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

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

This will log a message when MyClass is created.

What about method decorators? Any examples?

Absolutely! Here's an example of a method decorator:

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 executed with arg: ${arg}`);
    }
}

This will log the arguments whenever myMethod is called.

Can decorators be used with properties?

Yes, decorators can also be used with properties. Here's an example:

function ReadOnly(target: any, propertyName: string) {
    Object.defineProperty(target, propertyName, { writable: false });
}

class MyClass {
    @ReadOnly
    myProperty: string = 'This is read-only';
}

In this case, myProperty cannot be modified after it's set.