Objects

Question 1

Object

Answer 1

stores any number of values associated with string “keys”

var (name) = {

(key) : (value),
(key2) : (value2)

}

(name).(key) or (name)[“(key with spaces)”]

Question 2

Create an object, ‘me’, with the key of “name” with your name as a string. Add to the ‘me’ object a key of “age” and set it to your age, not as a string, but a number.

Answer 2

var me = {
        name: "Randy",
        age: 25
      };

Question 3

Method

Answer 3

a function that is a property of an object

(object).(key)((arg)) —> console.log

Question 4

this

Answer 4

• refers to the global object, window
• to be used only as a method

Question 5

On ‘andrew’ and ‘ryan’, set the ‘greet’ method as the ‘genericGreet’ function.

var genericGreet = function() {
 return "Hello, my name is " + this.name;
 }

var andrew = {
 name: "Andrew"
 }

var ryan = {
 name: "Ryan"
 }

Answer 5

var genericGreet = function() {
 return "Hello, my name is " + this.name;
 }

var andrew = {
 name: "Andrew",
 greet: genericGreet
 }

var ryan = {
 name: "Ryan",
 greet: genericGreet
 }

Question 6

Call vs. Apply

Answer 6

• call takes any # of args and puts it in context of this
• apply strictly takes an array of args

Question 7

Set the ‘greeting’ variable, by using the ‘genericGreet’ function in the context of ‘andrew’ with the array of arguments, ‘args1’.

var genericGreet = function(name, mood) {
 name = name || "you";
 mood = mood || "good";
 return "Hello " + name + ", my name is " + this.name +
 " and I am in a " + mood + " mood!";
 }

 var andrew = {
 name: "Andrew"
 }

var args1 = [“Michael”, “awesome”, “:)”];

var greeting = genericGreet;

Answer 7

var greeting = genericGreet.apply(andrew, args1);

if “name” is false or undefined, then || = “or” operator and uses “you”

Question 8

Prototype

Answer 8

an object that provides keys and values for another object

Question 9

Object Oriented Programming

Answer 9

programming based around creating and using objects

Question 10

Constructor Function

Answer 10

• special function for creating and initializing a new object
• always capitalize first letter

Question 11

new

Answer 11

creates new object, passes it to constructor function, and returns it

Question 12

Modify the ‘Car’ constructor function so that it takes an argument for its model and set its ‘model’ to the model passed in from the argument.

var carPrototype = {
model: “generic”,
currentGear: 0,
increaseGear: function() {
this.currentGear ++;
},
decreaseGear: function() {
this.currentGear–;
}
}

function Car() {

}

Answer 12

function Car(model) {
 this.model = model;
 }

Question 13

After the ‘Car’ constructor function, modify the Car’s prototype to be the ‘carPrototype’.

      function Car(model) {
        this.model = model;
      }

Answer 13

function Car(model) {
        this.model = model;
        Car.prototype = carPrototype;
      }

Question 14

Modify the Car’s prototype to have ‘wheels’ set to 4.

      function Car(model) {
        this.model = model;
        Car.prototype = carPrototype;
      }

Answer 14

function Car(model) {
        this.model = model;
        Car.prototype = carPrototype;
        Car.prototype.wheels = 4;
      }

Question 15

What are the values of mittens.name and mittens.legs after this code executes?

function Cat (name) {

this.name = name; this.ears = 2;

}

var mittens = new Cat(“Sir Mittens”);

Cat.prototype.legs = 4;

Answer 15

mittens. name === “Sir Mittens”;
mittens. legs = 4;

Question 16

How do call() and apply differ?

Answer 16

apply takes all the arguments as a single array, where call passes all arguments individually

Question 17

When a normal function is called, what is the value of “this”? (assuming the current JavaScript rules, not the upcoming version 5, or “strict mode”)

Answer 17

window

Question 18

Why do we name our construction functions with a leading capital letter?

Answer 18

it’s a convention which allows us to recognize where the “new” keyword should be used

Question 19

What does ‘this’ generally represent in a method?

Answer 19

the object to which the method belongs to

Question 20

What value would be displayed in the console for this code?

var person = {

name: “Mike”,
skills: [“html”, “css”]

}

person. name = “Bob”;
console. log(person[“name”]);

Answer 20

“Bob”

Question 21

What is a prototype?

Answer 21

it is an object that provides keys and values for another object, provided the other object does not itself define that key

Question 22

What is a disadvantage of using the bracket notation

( object[“key”] )

versus the dot notation

( object.key )?

Answer 22

the square bracket returns the object stored as the value, where dot notation instead returns a copy of the object which is the value