Introduction to Objects I | Codecademy

The "this" Keyword

Our setAge method works great for bob because it updates bob.age, but what if we want to use it for other people?

It turns out we can make a method work for many objects using a new keyword, this. The keyword this acts as a placeholder, and will refer to whichever object called that method when the method is actually used.

// here we define our method using "this", before we even introduce bob

var setAge = function (newAge) {

  this.age = newAge;

};

// now we make bob

var bob = new Object();

bob.age = 30;

// and down here we just use the method we already made

bob.setAge = setAge;

Let's look at the method setAge (line 2) to see how this works. By using the keyword this, setAge will change the age property of any object that calls it. Previously, we had a specific object bob instead of the keyword this. But that limited the use of the method to just bob.

Then when we say bob.setAge = setAge; (line 9), it means whenever we type bob.setAge( ), this.age in the setAge method will refer to bob.age.

Instructions

To show this way of making setAge works just like the one in exercise 2, use bob's setAge method to change his age to 50.

Stuck? Get a hint!

Just like in exercise 2, use bob.setAge(someNewAge); to use the method.