How to detect if a function is called as constructor

You can use new.target pseudo-property to detect whether a function was called as a constructor(using the new operator) or as a regular function call.

1. If a constructor or function invoked using the new operator, new.target returns a reference to the constructor or function.
2. For function calls, new.target is undefined.

 function Myfunc() {
   if (new.target) {
     console.log("called with new");
   } else {
     console.log("not called with new");
   }
 }

 new Myfunc(); // called with new
 Myfunc(); // not called with new
 Myfunc.call({}); // not called with new