Constructors in JavaScript objects

Question

Can JavaScript classes/objects have constructors? How are they created?

Answer 1

In JavaScript the invocation type defines the behaviour of the function:

• Direct invocation func()
• Method invocation on an object obj.func()
• Constructor invocation new func()
• Indirect invocation func.call() or func.apply()

---

The function is invoked as a constructor when calling using new operator:

function Cat(name) {
   this.name = name;
}
Cat.prototype.getName = function() {
   return this.name;
}

var myCat = new Cat('Sweet'); // Cat function invoked as a constructor

Any instance or prototype object in JavaScript have a property constructor, which refers to the constructor function.

Cat.prototype.constructor === Cat // => true
myCat.constructor         === Cat // => true

Check this post about constructor property.