Unfortunately it’s impossible to call original decorated function with context of object instance and that makes it particular useful

Assume we have simple Cat class similar to your example:

class Cat {

constructor(name) {

this.name = name

}

@somedecorator

meow() { return `${this.name} says Meow!` }

}

// And we’d like to extend result of the meow call

function somedecorator(target, name, descriptor) {

// target is Cat prototype here and not the instance

var fn = descriptor.value;

descriptor.value = function () {

var result = fn.call(target) // returns “undefined says Meow!”

return result + ‘ add something from decorator’

}

return descriptor;

}