JavaScript Basics Quiz
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Question 1/15
What does "NaN" stand for in JavaScript?
Select your answer
Question 2/15
What will the value of "x" be after the code is run?
let x = 5;
x = x * 2;
Select your answer
Question 3/15
How can you add a comment in JavaScript?
Select your answer
Question 4/15
In JavaScript, what will '2' + 2 evaluate to?
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Question 5/15
What is the output of the following JavaScript code?
var x = 10;
x += 5;
console.log(x);
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Question 6/15
What is a typical use case for the "isNaN()" function?
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Question 7/15
What does the "alert()" function do in JavaScript?
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Question 8/15
How do you round 7.25 to the nearest integer in JavaScript?
Math.round(7.25);
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Question 9/15
How do you write an "if" statement in JavaScript to execute some code if "i" is equal to 5?
if (i === 5) {
// code to execute
}
Select your answer
Question 10/15
How do you create a function in JavaScript?
function myFunction() {
// code here
}
Select your answer
Question 11/15
When the following code is executed, what will the value of the expression be?
3 == '3'
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Question 12/15
What is the correct way to declare a variable in JavaScript?
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Question 13/15
What will the following expression return: Boolean(0);
Boolean(0);
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Question 14/15
What is the correct syntax for referring to an external JavaScript file called 'app.js'?
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Question 15/15
What method is used to add new elements to the end of an array?
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Your Results
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Your Answers
Question 1/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
What does "NaN" stand for in JavaScript?
Available answers
NaN
stands for "Not-a-Number", indicating a value that is not a legal number.
Question 2/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
What will the value of "x" be after the code is run?
let x = 5;
x = x * 2;
Available answers
The operation
x = x * 2
assigns the result of 5 * 2
to x
, which is 10
.
Question 3/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
How can you add a comment in JavaScript?
Available answers
In JavaScript, comments start with
//
for single-line comments or /* ... */
for multi-line comments.
Question 4/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
In JavaScript, what will '2' + 2 evaluate to?
Available answers
In JavaScript, the expression
'2' + 2
results in the string '22' due to string concatenation.
Question 5/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
What is the output of the following JavaScript code?
var x = 10;
x += 5;
console.log(x);
Available answers
The code uses
+=
to add 5
to x
, giving 15
.
Question 6/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
What is a typical use case for the "isNaN()" function?
Available answers
The
isNaN()
function checks if a value is NaN (Not-a-Number).
Question 7/15
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answer was correct
🙁 Your
answer was incorrect
What does the "alert()" function do in JavaScript?
Available answers
The
alert()
function displays an alert box containing a specified message and an OK button.
Question 8/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
How do you round 7.25 to the nearest integer in JavaScript?
Math.round(7.25);
Available answers
To round a number in JavaScript, use
Math.round()
.
Question 9/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
How do you write an "if" statement in JavaScript to execute some code if "i" is equal to 5?
if (i === 5) {
// code to execute
}
Available answers
The syntax for an "if" statement in JavaScript to check for equality is:
if (i === 5) { /* code */ }
.
Question 10/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
How do you create a function in JavaScript?
function myFunction() {
// code here
}
Available answers
To define a function in JavaScript, use the syntax:
function myFunction() { /* code */ }
.
Question 11/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
When the following code is executed, what will the value of the expression be?
3 == '3'
Available answers
The
==
operator checks for equality with type coercion. Hence 3 == '3'
is true
.
Question 12/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
What is the correct way to declare a variable in JavaScript?
Available answers
In JavaScript, you declare a variable using the
var
, let
, or const
keyword, such as var myVariable;
.
Question 13/15
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answer was correct
🙁 Your
answer was incorrect
What will the following expression return: Boolean(0);
Boolean(0);
Available answers
The expression
Boolean(0)
returns false
because 0
is considered a "falsy" value in JavaScript.
Question 14/15
😊 Your
answer was correct
🙁 Your
answer was incorrect
What is the correct syntax for referring to an external JavaScript file called 'app.js'?
Available answers
To include an external JavaScript file, you use the
<script src='app.js'></script>
syntax.
Question 15/15
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answer was correct
🙁 Your
answer was incorrect
What method is used to add new elements to the end of an array?
Available answers
The
push()
method adds one or more elements to the end of an array.