Performance Measures MCQ question and answer in javascript with solution

21

Firebug is an extension of which browser?

A) Mozilla B) Chrome C) IE D) Opera

Discuss

Answer & Solution

Answer: Option A

Solution:

Firebug is an extension of Mozilla.

22

Firebug can be used to inspect

A) HTML B) CSS C) DOM D) All of the mentioned

Discuss

Answer & Solution

Answer: Option D

Solution:

Firebug is an extension for the Mozilla Firefox browser that allows you to debug and inspect HTML, CSS, the Document Object Model (DOM) and JavaScript.

23

Why do Web Developers use Firebug?

A) Track cookies B) Track sessions C) Both Track cookies and sessions D) None of the mentioned

Discuss

Answer & Solution

Answer: Option C

Solution:

Web developers use Firebug for the following reasons :
1. Inspect the behavior of HTML/CSS, and modify style & layout with true WYSIWYG 2. Debug JavaScript 3. Detect performance of website 4. Track Cookies & Sessions

24

What are the goals for using Firebug?

A) Performance B) Adaptability C) Complexity D) Reliability

Discuss

Answer & Solution

Answer: Option A

Solution:

The goals for using Firebug is :
1. Performance
2. Modularity
3. Shared code
4. Compatibility

25

Which of the following is not a feature of the User Interface?

A) Skinnable Interface B) Resizable Side Panel C) Fixed Side Panel D) Menu options

Discuss

Answer & Solution

Answer: Option C

Solution:

The features present in the User Interface are :
1. Port of Firebug’s Visual Object Representation (aka Reps)
2. Recreation of Firebug 1.3 User Interface with pixel precision
3. Menu options
4. Resizable Side Panel
5. Skinnable Interface

26

What is the default value of the property overrideConsole

A) 1 B) true C) 0 D) false

Discuss

Answer & Solution

Answer: Option B

Solution:

The default value of the property overrideConsole is true.

27

Which of the following property(s) has a default value as false?

A) disableWhenFirebugActive B) showIconWhenHidden C) disableXHRListener D) Both disableWhenFirebugActive & showIconWhenHidden

Discuss

Answer & Solution

Answer: Option C

Solution:

Only disableXHRListener property has a default value false. The properties disableWhenFirebugActive and showIconWhenHidden has a default value of true.

28

Which of the following action is possible in Firebug when used as a JavaScript Debugger and Profiler?

A) Pause execution in any line B) Find Scripts easily C) Find Scripts easily & also Pause execution in any line D) None of the mentioned

Discuss

Answer & Solution

Answer: Option C

Solution:

When Firebug is used as a JavaScript Debugger and Profiler, it can be used to find scripts easily and also pause the execution in any desired line.

29

The let keyword can be used

A) in a for or for/in loop, as a substitute for var B) as a block statement, to define new variables C) to define variables that are scoped to a single expression D) all of the mentioned

Discuss

Answer & Solution

Answer: Option D

Solution:

The let keyword can be used in four ways :
1. As a variable declaration like var;
2. In a for or for/in loop, as a substitute for var;
3. As a block statement, to define new variables and explicitly delimit their scope; and
4. To define variables that are scoped to a single expression.

30

How does PhantonJS use YSlow?

A) Queries B) Statements C) Command Line Prompt D) Command Line Script

Discuss

Answer & Solution

Answer: Option D

Solution:

Slow for PhantomJS is a command line script that allows page performance analysis from live URLs, unlike YSlow for Command Line (HAR) where a pre-generated HAR file is needed in order to analyze page performance.