Fundamentals of Front End Development MCQs with Answers
Practice important Fundamentals of Front End Development MCQs with answers and explanations.
Chapter: 86
Q961:
Fill in the blank: To improve performance, access a DOM element _____ and use it as a local variable.
A. multiple times
B. only once
C. every time
D. in a loop
Correct Answer:
B
Chapter: 86
Q962:
What should you do to reduce DOM access in JavaScript?
A. Access the DOM element once and store it in a variable
B. Access the DOM element multiple times
C. Avoid accessing the DOM
D. Use global variables
Correct Answer:
A
Chapter: 86
Q963:
What is an example of avoiding unnecessary variables in JavaScript?
A. Using local variables to store intermediate results
B. Creating a new variable for every calculation
C. Combining values directly in statements
D. Declaring variables globally
Correct Answer:
C
Chapter: 86
Q964:
Fill in the blank: Delaying JavaScript loading by placing scripts at the _____ of the page body improves page load performance.
A. top
B. middle
C. bottom
D. side
Correct Answer:
C
Chapter: 86
Q965:
What does the defer attribute do when used in a script tag?
A. Executes the script immediately
B. Executes the script before the page is parsed
C. Executes the script after the page has finished parsing
D. Prevents the script from loading
Correct Answer:
C
Chapter: 86
Q966:
What is a more efficient way to handle JavaScript loading according to best practices?
A. Place scripts at the top of the page
B. Use the defer attribute for external scripts
C. Use synchronous script loading
D. Use the with keyword for better speed
Correct Answer:
B
Chapter: 86
Q967:
Fill in the blank: To avoid using the with keyword, which has a negative effect on speed, _____ .
A. use local variables
B. use global variables
C. avoid variable declarations
D. use the let keyword
Correct Answer:
A
Chapter: 86
Q968:
What should you do if you need to add a script to the page after it has loaded?
A. Use document.createElement and append the script
B. Add the script tag in the head section
C. Use the defer attribute
D. Use the async attribute
Correct Answer:
A
Chapter: 86
Q969:
Fill in the blank: To improve performance, avoid creating _____ if you don't plan to use them.
A. global variables
B. unnecessary variables
C. local variables
D. arrays
Correct Answer:
B
Chapter: 86
Q970:
What is one way to handle DOM size for better performance?
A. Increase the number of DOM elements
B. Reduce the number of DOM elements
C. Add more scripts to the DOM
D. Use more complex DOM structures
Correct Answer:
B
Chapter: 86
Q971:
What is the impact of placing JavaScript at the bottom of the page body?
A. It blocks other downloads
B. It allows for faster script execution
C. It ensures the page loads faster
D. It delays the script execution
Correct Answer:
C
Chapter: 87
Q972:
Which ECMAScript version was released in December 2009?
A. ES4
B. ES5
C. ES6
D. ES3
Correct Answer:
B
Chapter: 87
Q973:
Fill in the blank: The latest official version of JavaScript as of June 2015 is _____ .
A. ES4
B. ES5
C. ES6
D. ES3
Correct Answer:
C
Chapter: 87
Q974:
What should you avoid using as variables or function names in JavaScript?
A. Reserved words
B. Variable names
C. Function names
D. Object properties
Correct Answer:
A
Chapter: 87
Q975:
What is a reserved word in JavaScript that cannot be used as a variable name?
A. let
B. const
C. this
D. import
Correct Answer:
C
Chapter: 87
Q976:
Fill in the blank: In JavaScript, you should avoid using _____ as identifiers for variables or functions.
A. standard words
B. reserved words
C. common words
D. variable names
Correct Answer:
B
Chapter: 87
Q977:
What is a nonstandard keyword used in some JavaScript implementations?
A. var
B. const
C. break
D. import
Correct Answer:
B
Chapter: 87
Q978:
Fill in the blank: The const keyword is treated as a synonym for _____ in some JavaScript engines.
A. let
B. var
C. this
D. export
Correct Answer:
B
Chapter: 87
Q979:
What should be avoided when naming variables or functions in JavaScript?
A. Java reserved words
B. HTML event handlers
C. Common JavaScript functions
D. Nonstandard keywords
Correct Answer:
A
Chapter: 87
Q980:
Fill in the blank: The JavaScript reserved word _____ cannot be used as a variable name.
A. eval
B. import
C. extends
D. package
Correct Answer:
A