JS 2

Question 1

What is a method?

Answer 1

a function which is a property of an object

Question 2

How can you tell the difference between a method definition and a method call?

Answer 2

• a method definition has function definition and code block

- a method call is like a function call with object name dot and method name followed by parenthesis

Question 3

Describe method definition syntax (structure).

Answer 3

• defined as a property with a value of a function in an object literal {methodName: function () {}}
• after the object’s creation, a function could be assigned to the method name’s property of the object objectName.methodName = function () {}

Question 4

Describe method call syntax (structure).

Answer 4

object name, dot, method name, parenthesis

objectName.methodName()

Question 5

How is a method different from any other function?

Answer 5

need dot or bracket notation to see what object the method in

Question 6

What is the defining characteristic of Object-Oriented Programming?

Answer 6

• objects can contain both properties and methods

- data and behavior are combined

Question 7

What are 4 principles of OOP?

Answer 7

Abstraction
Encapsulation
Inheritance
Polymorphism

Question 8

What is “abstraction”?

Answer 8

• removing temporal details to focus on details of greater importance
• able to work with complex process in simple ways

Question 9

What does API stand for?

Answer 9

application programming interface

Question 10

What is the purpose of an API?

Answer 10

• allows users to use interface independently of implementation
• can use something without knowing how it was built

Question 11

What is ‘this’ in JavaScript?

Answer 11

a property of an execution context that is a reference to its enclosing object

Question 12

What does it mean to say that ‘this’ is an “implicit parameter”?

Answer 12

‘this’ is available in a function’s code block, even though it was never explicitly declared

Question 13

When is the value of this determined in a function; call time or definition time?

Answer 13

call time

Question 14

How can you tell what the value of this will be for a particular function or method definition?

Answer 14

you don’t know until it is called

Question 15

How can you tell what the value of this is for a particular function or method call?

Answer 15

• if it is in a method inside an object, then it refers to that object
• if it is in a function inside the global scope, then it refers to Window

Question 16

What kind of inheritance does the JavaScript programming language use?

Answer 16

prototypical inheritance, which is reusing objects as prototypes to allow for the inheritance of methods and properties

Question 17

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 17

those methods are defined on those elements’ __proto__ property

Question 18

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

Answer 18

looks for it on the prototype object which it is inheriting properties/methods from

Question 19

What does the new operator do?

Answer 19

1. creates an instance object from a constructor function
2. sets prototype for that object
3. passes the object as “this”
4. object that was created is returned

Question 20

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

Answer 20

prototype property

Question 21

What does the instanceof operator do?

Answer 21

• tests to see if the prototype property of a constructor appears in the prototype chain of an object
• returns a boolean whether it is an instance or not