JS Prototypes & JS Constructors

Question 1

What kind of inheritance does the JavaScript programming language use?

Answer 1

JS uses prototype-based inheritance

Question 2

How is it possible to call methods on strings, arrays, and numbers even though those methods don’t actually exist on objects, arrays, and numbers?

Answer 2

Due to JS prototypes; models that was created that contain these methods.

Question 3

If an object does not have its own property or method by a given key, where does JavaScript look for it?

Answer 3

From the object’s prototype, if it’s not there then object’s object’s prototype

Question 4

What does the <b>new</b> operator do?

Answer 4

<ul>The new keyword does the following things:
<li>Creates a blank, plain JavaScript object</li>
<li>Links (sets the constructor of) the newly created object to another object by setting the other object as its parent prototype;</li>
<li>Passes the newly created object from Step 1 as the this context;</li>
<li>Returns this if the function doesn't return an object.</li>
</ul>

Question 5

What property of JavaScript functions can store shared behavior for instances created with <b>new</b>?

Answer 5

Prototype property

Question 6

What does the <b>instanceof</b> operator do?

Answer 6

It tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object. Returns a boolean.