JavaScript Constructors

Question 1

What does the new operator do?

Answer 1

lets developers create an instance of a user-defined object type or of one of the built-in object types that has a constructor function.

1. Creates a blank, plain JavaScript object.
2. Adds a property to the new object (__proto__) that links to the constructor function’s prototype object
3. Binds the newly created object instance as the this context (i.e. all references to this in the constructor function now refer to the object created in the first step).
4. Returns this if the function doesn’t return an object.

Question 2

What property of JavaScript functions can store shared behavior for instances created with new?

Answer 2

prototype property - which defines a property that is shared by all objects created with that function

You can add a shared property to a previously defined object type by using the prototype property

Question 3

What does the instanceof operator do?

Answer 3

Operator tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object. The return value is a boolean value.