How do I create custom decorators in JavaScript?

How do I create custom decorators in JavaScript?

Creating custom decorators in JavaScript involves using the decorator syntax to modify classes or methods. Would you like a basic example?

Yes, please provide a simple example.

Sure! Here's a basic example of a method decorator:

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
    sayHello(name) {
        return `Hello, ${name}!`;
    }
}

const example = new Example();
example.sayHello('Alice');

This decorator logs the arguments passed to the method before executing it.

What if I want to create a class decorator instead?

For a class decorator, you can modify the class itself. Here's an example:

function addTimestamp(target) {
    target.prototype.timestamp = new Date();
}

@addTimestamp
class MyClass {}

const instance = new MyClass();
console.log(instance.timestamp); // Logs the current timestamp

This decorator adds a timestamp property to the class.