Chapter 10 : JavaScript Part 3

Question 1

What information does the window.screen object contains?

Answer 1

1. Information about the user’s screen

• It can be written without the window prefix

screen.width
screen.height

Question 2

What value does screen.width returns?

Answer 2

1. Returns the width of the visitor’s screen in pixels

Question 3

What value does screen.height returns?

Answer 3

1. Returns the height of the visitor’s screen in pixels

Question 4

What value does screen.availWidth returns?

Answer 4

1. Returns the width of the visitor’s screen ( pixels ), minus interface features like the windows taskbar

Question 5

What value does screen.availHeight returns?

Answer 5

1. Returns the height of the visitor’s screen ( pixels ), minus interface features like the windows taskbar

Question 6

What value does screen.colorDepth returns?

Answer 6

1. Returns the number of bits used to display 1 color

Question 7

What value does screen.pixelDepth returns?

Answer 7

1. Returns the pixel depth of the screen

Question 8

Write a JavaScript code to view screen width and height with id demo and demo2?

Answer 8

<script>
document.getElementById("demo").innerHTML = "Screen Width  : " + screen.width;
document.getElementById("demo2").innerHTML = "Screen Height  : " + screen.height;
</script>

<p></p>

<p></p>

Question 9

Write a JavaScript code to view screen available width and height with id demo and demo2?

Answer 9

<script>
document.getElementById("demo").innerHTML = "Screen Avail Width  : " + screen.availWidth;
document.getElementById("demo2").innerHTML = "Screen Avail Height  : " + screen.availHeight;
</script>

<p></p>

<p></p>

Question 10

Write a JavaScript code to view color depth and pixel depth with id demo and demo2?

Answer 10

<script>
document.getElementById("demo").innerHTML = "Color Depth  : " + screen.colorDepth;
document.getElementById("demo2").innerHTML = "Pixel Depth  : " + screen.pixelDepth;
</script>

<p></p>

<p></p>

Question 11

What can window.location object be used?

Answer 11

1. Used to get the current page address ( URL ) and to redirect the browser to a new page

• It can also be written without using the window prefix
  window.location.href -> location.href

Question 12

What does window.location.href do and what does it return?

Answer 12

1. Returns the href ( URL ) of the current page
2. http://www.apu.edu.my/index.html

Question 13

What does window.location.hostname do and what does it return?

Answer 13

1. Returns the domain name of the web host
2. www.apu.edu.my

Question 14

What does window.location.[athname do and what does it return?

Answer 14

1. Returns the path and filename of the current page
2. /explore-apu/university/index.html

Question 15

What does window.location.protocol do and what does it return?

Answer 15

1. Returns the web protocol used
2. http : / https:

Question 16

What does window.location.assign() do and what does it return?

Answer 16

1. Loads a new document
2. Loads a new document on current document

Question 17

What object contains the browsers history?

Answer 17

1. window.history

• It can also be written without the window prefix

Question 18

List out 2 methods for how JavaScript can access user browsing history

Answer 18

1. history.back()
2. history.forward()

• There are some limitations to protect the privacy of the users

Question 19

What are the time intevals called and what can it do?

Answer 19

1. Timing Events
2. Execution of code at specified time intervals

Question 20

List out 2 key methods for Timing Events

Answer 20

1. setTimeout ( function , milliseconds)
   
   • Executes a function after waiting a specified number of milliseconds
2. setInterval ( function, milliseconds )
   
   • Same as setTimeout but repeats the execution of the function

<button>Try it</button>

<button>Try it</button>

• Can also use with window prefix

<button>Try it</button>

Question 21

What does clearTimeout() do?

Answer 21

1. Stops the execution of the function specified in setTimeout()

Question 22

What is the syntax for clearTimeout?

Answer 22

1. window.clearTimeout(timeoutVariable)
2. clearTimeout(timeoutVariable)

• Uses the variable returned from setTimeout()

myVar = setTimeout(function, milliseconds);
clearTimeout(myVar);

• We can also stop the execution by calling the clearTimeout() method

Question 23

What method can we use to stop the setInterval() method?

Answer 23

1. clearInterval()

• myVar = setInverval( function, milliseconds );
  clearInterval(myVar);

Question 24

What does cookies do?

Answer 24

1. Allow website to store user information in web page for faster login, performance

• Data stored in small text files , on user’s computer

Question 25

What problem does cookies solved?

Answer 25

1. How to remember information about the user

Question 26

What JavaScript property is used to store cookies?

Answer 26

1. document.cookie

Question 27

How to create cookie to store username John Doe?

Answer 27

document.cookie = “username=John Doe”;

Question 28

Set the cookie username John Doe and expiry date and then the path

Answer 28

document.cookie = “username=John Doe”; expires = Thu, 18 Dec 2017 12:00:00 UTC ; path=”/”;

Question 29

What is the default value for path?

Answer 29

1. By default, the cookie belongs to the current page

Question 30

How to read the cookie?

Answer 30

var username = document.cookie;

• document.coockie will return all cookies in one string like
  cookie1 = value ; cookie2 = value ; cookie3 = value