Wednesday July 22

Questions from Last Night's Reading

• When would we use prototype? (Shared functionality)
• if [] are {} then what's the difference (instanceof)
• prototype vs assignment and regular {} (Constructors)
• Prototypes and Scope (private variables)
• Getters and Setters

Outline

• this with regular objects
• returning objects from functions
• Basic constructors
• Basic prototype inheritance
• Overriding Prototype Functions
• Private Variables

Exercises

• MathArray Prototype
• US Citizen (private SSN)

Suggested Reading

There's been still some confusion about "what is a function", "what does a method mean", "what does property mean". So, if you ask any of those questions and can't answer quickly, then read:

• Objects and Properties
• Constructors
• Prototype
• instanceof
• Functions
• this

Extra Reading

Once again, try reading the Eloquent Javascript chapters from the last two days:

• Prototypes and Objects
• Values
• Numbers
• Arithmetic
• Variables
• Defining A Function

Homework

Tonight you will be working on the prototype exercise:

• https://github.com/tiy-lr-fee-2015-June/assignments/tree/master/4.3-prototypes

Getting Started on HW

Setup for tonight's HW

• Create new folder 4.3-prototypes
• Initialize git in this new project
• Copy constructors.js
• Create .jscsrc and set things up for Airbnb code style
• Commit to master
• Create github repo (hub create)
• Push
• Switch to develop
• Succeed!

Gems from the Slackiverse

Since Slack isn't permanent I will try to start copying some of the most helpful questions and answers from the slack rooms:

Better Prompt for Question 4

// Create a constructor called `KeepSecret`. The constructor function
// itself should accept a parameter called `secret` it should keep this
// as a private variable. Add a function to `KeepSecret` that is called
// `squeal` that returns the secret string.

Better Prompt for Question 5

// Create a constructor called `Key`. Create another constructor
// called `Safe`. Make the Safe constructor take 2 arguments. The
// first argument can be any piece if data to keep safe. This must
// be stored using a private variable like you did with KeepSecret.
// The 2nd param to the `Safe` constructor needs to be an instance
// of `Key` you need to store it as a private variable. Then, add a
// function to the Safe prototype called `unlock` that accepts a key. 
// If the key matches the key that was used to create the Safe; then
// return the secret data.

What is a property?

When we talk about a property all we mean is that there is a value on an object.

If I want a property called say on a Dog equal to life if rough, then I should be able to run var d = new Dog() and when I check the value say it should always return life is rough.

What is a method?

When we talk about a method that just means that there is a function available on an object.

So if an assignment says that a Cat should have a method growl, I should be able to create a Cat with var c = new Cat() and then run c.growl().