2. IF JavaScript

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Questions and Answers

What will be logged to the console when age is set to 0 and evaluated with the condition 'if(age){ ... }'?

The code will not run.

Variable is defined.

Variable has NOT been defined. (correct)

An error will occur.

In the expression 'let myCity = city || defaultCity;', what value will myCity have if city is undefined?

null

Vilnius (correct)

Kaunas

undefined

What does the statement 'console.log(false || true);' evaluate to?

undefined

true (correct)

null

false

When logically evaluating 'console.log("abc" || "");', what will be the output?

abc Signup and view all the answers

Which of the following statements about the value `NaN` is true?

NaN is a falsy value. Signup and view all the answers

What will the output be if the value of 'a' is 2 + 2 in the provided switch statement?

Exactly! Signup and view all the answers

Which statement about the use of 'break' in the switch statement is true?

It stops the execution of the switch after a matching case. Signup and view all the answers

Which of the following is NOT considered a falsy value?

'0' Signup and view all the answers

What will happen if there is no break statement after case 4 in the switch?

The next case will be executed consecutively. Signup and view all the answers

In a Boolean context, which type of value is treated as true?

1 Signup and view all the answers

What is the result of the comparison operation alert(2 > 1)?

true Signup and view all the answers

When comparing two strings, what is the first step in the algorithm?

Compare the first character of both strings. Signup and view all the answers

What boolean value is returned when executing alert(2 == 1)?

false Signup and view all the answers

In the statement if (year == 2022), what type of value does the condition evaluate?

Boolean Signup and view all the answers

What does the expression console.log(3 > 2 > 1) return?

false Signup and view all the answers

Which logical operator would return true only if both operands are true?

AND Signup and view all the answers

Why is the comparison between two strings done character by character?

To find the first differing character. Signup and view all the answers

Which of the following statements is true regarding the boolean values in JavaScript?

Both true and false can be represented as strings. Signup and view all the answers

What will the alert display if the user inputs '2014' in the if-else statement checking for the year 2015?

Too early... Signup and view all the answers

In the conditional operator example, what does the expression 'age > 18 ? true : false' evaluate to if age is 20?

true Signup and view all the answers

When using AND (&&), what is the outcome if one operand is false?

The entire expression is false. Signup and view all the answers

What will happen if 'hour' is set to 20 and the condition 'if (hour < 10 || hour > 18)' is evaluated?

The office is closed. Signup and view all the answers

What does the else if clause allow you to do in an if-else structure?

Specify multiple conditions in a single if statement. Signup and view all the answers

What will the alert display if the variable accessAllowed is set to true?

true Signup and view all the answers

In the statement 'alert(accessAllowed)', what information is conveyed when accessAllowed is false?

The user is denied access. Signup and view all the answers

What will occur in an if statement using logical NOT (!) before a variable that is truthy?

The condition will evaluate to false. Signup and view all the answers

Study Notes

JavaScript Fundamentals

JavaScript is a programming language, used to create interactive web pages
Comparison operators allow comparing values
== (equal to) checks only value
=== (equal in value and type) checks value and type
!= (not equal to) checks only value
!== (not equal in value or type) checks value and type
> (greater than)
< (less than)
>= (greater than or equal to)
<= (less than or equal to)

Boolean Types

Boolean values represent logical states
true or false

Conditional Statements

if-else statements control program flow, based on conditions
If the condition result is true the block of code is executed
switch statements handle multiple conditions
The switch statement checks if a given variable or expression equals a case value and then executes the statements associated with that case. If no matching case is found, the optional default statements may be executed.

Logical Operators

Logical operators combine conditions using Boolean logic to evaluate to true or false
|| (OR): Returns true if at least one operand is true
&& (AND): Returns true if both operands are true
! (NOT): Negates a Boolean expression (e.g., !true is false)

Conditional Operator (Ternary Operator)

The conditional operator '? :' provides a compact way to express an if-else statement
condition ? expression1 : expression2

Falsy Values

Certain values in JavaScript are considered false when used in a Boolean context
Examples include false, null, undefined, 0, -0, NaN, '' (empty string)
if statement conditional tests if a variable is defined or not

Functions

Functions are reusable blocks of code, accepting parameters and returning values
Parameters are values passed to a function (inputs)
Functions perform actions via their function body
Functions may return a value to the function's caller

Practical examples

Various example code snippets showing practical applications of these concepts are provided in slides (e.g. using prompt, alert, and console.log).

Studying That Suits You

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Description

This quiz covers the foundational concepts of JavaScript, including comparison and logical operators, boolean types, and conditional statements. Test your understanding of these essential programming principles that allow you to create interactive web applications.

2. IF JavaScript

Choose a study mode

Podcast

Questions and Answers

What will be logged to the console when age is set to 0 and evaluated with the condition 'if(age){ ... }'?

In the expression 'let myCity = city || defaultCity;', what value will myCity have if city is undefined?

What does the statement 'console.log(false || true);' evaluate to?

When logically evaluating 'console.log("abc" || "");', what will be the output?

Which of the following statements about the value NaN is true?

What will the output be if the value of 'a' is 2 + 2 in the provided switch statement?

Which statement about the use of 'break' in the switch statement is true?

Which of the following is NOT considered a falsy value?

What will happen if there is no break statement after case 4 in the switch?

In a Boolean context, which type of value is treated as true?

What is the result of the comparison operation alert(2 > 1)?

When comparing two strings, what is the first step in the algorithm?

What boolean value is returned when executing alert(2 == 1)?

In the statement if (year == 2022), what type of value does the condition evaluate?

What does the expression console.log(3 > 2 > 1) return?

Which logical operator would return true only if both operands are true?

Why is the comparison between two strings done character by character?

Which of the following statements is true regarding the boolean values in JavaScript?

What will the alert display if the user inputs '2014' in the if-else statement checking for the year 2015?

In the conditional operator example, what does the expression 'age > 18 ? true : false' evaluate to if age is 20?

When using AND (&&), what is the outcome if one operand is false?

What will happen if 'hour' is set to 20 and the condition 'if (hour < 10 || hour > 18)' is evaluated?

What does the else if clause allow you to do in an if-else structure?

What will the alert display if the variable accessAllowed is set to true?

In the statement 'alert(accessAllowed)', what information is conveyed when accessAllowed is false?

What will occur in an if statement using logical NOT (!) before a variable that is truthy?

Study Notes

JavaScript Fundamentals

Boolean Types

Conditional Statements

Logical Operators

Conditional Operator (Ternary Operator)

Falsy Values

Functions

Practical examples

Studying That Suits You

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