TypeScript class decorator that modifies object instance

Why not just assign those properties to the prototype, and subsequently assign to the instance on first invocation

// decoratorfunction addAndCall(cb: Function, newField: string) {  // cb is now available in the decorator  return function(ctor: Function): void {    Object.defineProperty(ctor.prototype, newField, {      value: function(...args: any[]) {        return Object.defineProperty(this, newField, {          value: function(...args: any[]) {            console.log(newField, ...args);          }        })[newField](...args);      }    });    cb(ctor);  }}let callMe = (decoratedCtor) => console.log(decoratedCtor);@addAndCall(callMe, 'propertyName')class AddToMe {}let addToMe = new AddToMe();(<any>addToMe).propertyName(1, 2);

Here's a working version:

function addAndCall(target: any) {    var original = target;    function construct(constructor, args) {        var c: any = function () {            this.newAttribute = "object instance value";            ExternalModule.externalFunction(this);            return constructor.apply(this, args);;        }        c.prototype = constructor.prototype;        return new c();    }    var f: any = function (...args) {        return construct(original, args);    }    f.prototype = original.prototype;    return f;}

(code in playground)