March 11, 2001 - Checking for a Prototype Chain

Yehuda Shiran March 11, 2001
Checking for a Prototype Chain
Tips: March 2001

Yehuda Shiran, Ph.D.
Doc JavaScript

Use the isPrototypeOf() method to find out if object2 had object1 in its prototype chain:

object1.prototype.isPrototypeOf(0bject2);
It returns true if object2 is an object and when object1 appears in the prototype chain of object2. Let's look at an example:

function Person() {
  this.name = "Rob Roberson";
  this.age = 31;
}
function Employee() {
  this.dept = "HR";
  this.manager = "John Johnson";
}
Employee.prototype = new Person();
var Ken = new Employee();

Ken is in the prototype chain of Employee, Person, and Object. Prove it to yourself by clicking on each class. They alert Employee.prototype.isPrototypeOf(Ken), Person.prototype.isPrototypeOf(Ken), and Object.prototype.isPrototypeOf(Ken), respectively.