If we create an object called 'a' from a function constructor, then why is 'a' not an instance of Function?

Question

function person(first, last, age, eye) {
    this.firstName = first;
    this.lastName = last;
    this.age = age;
    this.eyeColor = eye;
}
var myFather = new person("John", "Doe", 50, "blue");
console.log(myFather instanceof person); //true
console.log(myFather instanceof Object); //true
console.log(myFather instanceof Function); //false

Hello, in this case, we created an object from the function constructor: 'person'.

Every function in JavaScript is an instance of the Function constructor. Why is myFather not an instance of Function?

Because the object referenced by `myFather` is a plain object *created* by the `person()` constructor. When you call a function with `new`, a new object is created and bound to `this` in the constructor context. — Pointy, Jul 08 '17 at 12:59
The prototype chain is myFather -> person.prototype -> object.prototype . instanceof checks for that — Jonas Wilms, Jul 08 '17 at 13:17

score 3 · Accepted Answer · answered Jul 08 '17 at 13:01

myFather is an object instance of person that is why it is returning true for myFather instanceof Object but false for myFather instanceof Function as it is not a function but an object, you can't call myFather again to instantiate another object. Actually person is an instance of Function. When you call new person a plain object is returned and it is stored in myFather.

function person(first, last, age, eye) {
    this.firstName = first;
    this.lastName = last;
    this.age = age;
    this.eyeColor = eye;
}
var myFather = new person("John", "Doe", 50, "blue");
console.log(myFather instanceof person); //true
console.log(myFather instanceof Object); //true
console.log(myFather instanceof Function); //false
console.log(person instanceof Function); //true

ah ok, I got it now. Thanks a lot – thelearner Jul 08 '17 at 13:03 — thelearner, Jul 08 '17 at 13:03

If we create an object called 'a' from a function constructor, then why is 'a' not an instance of Function?

1 Answers1