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As developers include more interactivity and complexity into their programs, JavaScript has become an essential part of the Internet experience. It is required for search engines, e-commerce, content management systems, responsive design, social media, and phone applications to function. PayPal uses JavaScript on the front end of their website for quite some time. Microsoft also uses JavaScript to build its Edge web browser.
Thus Mobiprep has curated a list of top 40 JavaScript placement questions and answers which can help you ace the placement process.
Basic JavaScript Placement Questions
Q1. What are the three important manipulations done in for loop on a loop variable?
Updation, Incrementation, Initialization
Initialization, Testing, Updation
Testing, Updation, Testing
Initialization, Testing, Incrementation
Answer
Correct Answer: A Explanation: In for loop, firstly the loop initializes the variable then test the condition and then after executing the statement increments its value.
Q2. A function definition expression can be called as:
Function prototype
Function literal
Function calling
Answer
Correct Answer: B Explanation: A function definition expression is a “function literal” .A Function definition expression typically consists of the keyword function followed by a comma-separated list of zero or more identifiers (the parameter names) in parentheses and a block of JavaScript code (the function body) in curly braces.
Q3. The expression of calling (or executing) a function or method in JavaScript is called :
Primary expression
Functional expression
Invocation expression
Answer
Correct Answer: C Explanation: An invocation expression is JavaScript’s syntax for calling (or executing) a function (or method). It starts with a function expression that identifies the function to be called.
Q4. The script tag must be placed in __________
the head tag
the head or body
the title or head
after the body tag
Answer
Correct Answer: B Explanation: If the script tag is placed after the body tag, then, it will not be evaluated at all. Also, it is always recommended and effective to use the script snippet in the <head> tag.
Q5. The four kinds of class members are ________
Instance methods, Instance fields, Static method, Dynamic method
Instance fields, Instance methods, Class fields, Class methods
Instance fields, Non-instance fields, Dynamic methods, Global methods
Global methods, Local methods, Dynamic methods, Static methods
Answer
Correct Answer: B Explanation: A class mainly contains data members and associated member functions. Therefore over all different kinds of class members are instance field, instance method, class fields and class methods.
Q6. The scope of a function is also called as ________
Predefined function
Module function
Public function
Private function
Answer
Correct Answer: B Explanation: The scope of a function can be used as a private namespace for a module. Therefore, the scope of a function is called a module function.
Q7. The basic difference between JavaScript and Java is _________
There is no difference
Functions are considered as fields
Variables are specific
Functions are values, and there is no hard distinction between methods and fields
Answer
Correct Answer: D
Explanation: Java is an OOP programming language while JavaScript is an OOP scripting language. The basic difference between JavaScript and Java is that the functions are values, and there is no hard distinction between methods and fields.
Q8.The regular expression to match any one character not between the brackets is:
[…]
[^]
[^…]
[\D]
Answer
Correct Answer: C
Explanation: RegExp defines a special set of character that is used to do manipulation on strings and other variables. The [^…] character class is used to match or draw any one character not between the brackets
Q9. What are the events generated by the Node objects called?
Generators
Emitters
Dispatchers
High events
Answer
Correct Answer: B Explanation: There are two classes of events one is called event listener and the other is called event emitter. Node objects that generate events (known as event emitters) define an on() method for registering handlers.
Q10. Which of the following is an event emitter?
Once
Process
Listeners
On
Answer
Correct Answer: B Explanation: The process object is an event emitter. The Node defines other important global under the process namespaces that contain properties of that object like version, argv, env, pid, getuid(), cwd(), chdir() and exit().
Q11. Which is the function used to retrieve a value?
get()
retrieve()
getItem()
retrieveItem()
Answer
Correct Answer: C Explanation: To retrieve a value, pass the name to getItem(). The getItem() method of the Storage interface, when passed a key name, will return that key’s value, or null if the key does not exist, in the given Storage object
Q12. What is the method used to pause “data” events?
s.pause();
s.stop();
s.halt();
s.wait();
Answer
Correct Answer: A
Explanation: Data events are the events which are performed by either the user or the browser.
Q13. Which is the handler method used to invoke when uncaught JavaScript exceptions occur?
Onhalt
Onerror
Both onhalt and onerror
Onsuspend
Answer
Correct Answer: B
Explanation: The onerror handler method can be registered to be invoked when uncaught JavaScript exceptions occur. The onerror event is triggered if an error occurs while loading an external file (e.g. a document or an image).
Q14.The paragraph “p” is a part of __________
a) h1
b) body
c) html
d) both body and html
Answer
Correct Answer: D Explanation: The paragraph tag belongs to both html and body tag. It is used to write paragraph on html pages.
Q15. The URL property belongs to which of the following object?
Document
Element
Location
Event
Answer
Correct Answer: A
Explanation: The Document object has a URL property, which is a static string that holds the URL of the document when it was first loaded. If you want to access any element in an HTML page, you always start with accessing the document object.
For more JavaScript placement questions and answers download our free handbook below.
Mobiprep handbooks are free downloadable placement preparation resources that can help you ace any company placement process. We have curated a list of the 40 most important MCQ questions with detailed explanations to ensure the best placement preparation.