[typescript]decorator

https://stackoverflow.com/questions/29775830/how-to-implement-a-typescript-decorator

General Points

• Decorators are called when the class is declared—not when an object is instantiated.
• Multiple decorators can be defined on the same Class/Property/Method/Parameter.
• Decorators are not allowed on constructors.

function editable(isEdit:boolean){
    return function(target:any, propName:string,description:PropertyDescriptor){
        console.log(target);
        console.log('propName:'+propName);
        console.log(description);
 
        target.heyjude = 'heyjude';
    }
}
 
 
class Person{
    constructor(){
        console.log('new Person():');
    }
 
    @editable(true)
    hello(){
        console.log('hello');
    }
}
 
const person = new Person();
person.hello();
console.log(person.heyjude);
 
 
// Person {}
// propName:hello
// { value: [Function: hello],
//     writable: true,
//         enumerable: false,
//     configurable: true }
// new Person():
// heyjude
 

• target: The prototype of the class (Object).
• propertyKey: The name of the method (string | symbol).
• descriptor: A TypedPropertyDescriptor — If you're unfamiliar with a descriptor's keys, I would recommend reading about it in this documentation on Object.defineProperty (it's the third parameter).

※decorator는 선언과 동시에 콜되기 때문에, const person = new Person();초기화되지 않아도 class Person{...}만으로 실행된다.