What are decorators in programming languages?

What are decorators in programming languages?

Decorators are a design pattern used to add new functionality to existing objects in a flexible way. They are commonly used in languages like Python, JavaScript, and Java.

Can you give me an example of a decorator in Python?

Sure! In Python, a decorator is a function that takes another function and extends its behavior without explicitly modifying it. For example:

def my_decorator(func):
    def wrapper():
        print("Something is happening before the function is called.")
        func()
        print("Something is happening after the function is called.")
    return wrapper

@my_decorator
def say_hello():
    print("Hello!")

say_hello()

How do decorators work in JavaScript?

In JavaScript, decorators are a proposed feature that allows you to modify classes and class methods. They can be used to add metadata or modify behavior. Here's a simple example:

function log(target, key, descriptor) {
    const originalMethod = descriptor.value;
    descriptor.value = function(...args) {
        console.log(`Calling ${key} with`, args);
        return originalMethod.apply(this, args);
    };
    return descriptor;
}

class Example {
    @log
    method(arg) {
        console.log(`Method called with ${arg}`);
    }
}

const example = new Example();
example.method('test');