en.javascript.info/1-js/9-object-inheritance/07-constructor-property/4-new-object-same-constructor/solution.md

We can use such approach if we are sure that "constructor" property has the correct value.

For instance, if we don't touch the default "prototype", then this code works for sure:

function User(name) {
  this.name = name;
}

let user = new User('John');
let user2 = new user.constructor('Pete');

alert( user2.name ); // Pete (worked!)

It worked, because User.prototype.constructor == User.

..But if someone, so to say, overwrites User.prototype and forgets to recreate "constructor", then it would fail.

For instance:

function User(name) {
  this.name = name;
}
*!*
User.prototype = {}; // (*)
*/!*

let user = new User('John');
let user2 = new user.constructor('Pete');

alert( user2.name ); // undefined

Why user2.name is undefined?

Here's how new user.constructor('Pete') works:

1. First, it looks for constructor in user. Nothing.
2. Then it follows the prototype chain. The prototype of user is User.prototype, and it also has nothing.
3. The value of User.prototype is a plain object {}, it's prototype is Object.prototype. And there is Object.prototype.constructor == Object. So it is used.

At the end, we have let user2 = new Object('Pete'). The built-in Object constructor ignores arguments, it always creates an empty object -- that's what we have in user2 after all.