JavaScript Basics

What keyword is used to declare a variable in JavaScript?

• var

• function

• let

• const

Answer explanation

The keyword 'let' is used to declare a variable in JavaScript.

Which loop is used to iterate over an array in JavaScript?

• while

• switch

• if

• for

Answer explanation

The correct loop used to iterate over an array in JavaScript is the 'for' loop.

What symbol is used for strict equality comparison in JavaScript?

• ===

• =/=

• !==

• ===

Answer explanation

The symbol used for strict equality comparison in JavaScript is '===' which checks both value and type.

How do you write an 'if' statement in JavaScript?

• if (condition) // code block

• if [condition] { // code block }

• if (condition) { // code block }

• if (condition) { /* code block */ }

Answer explanation

In JavaScript, the correct way to write an 'if' statement is: if (condition) { // code block }

What is the result of 10 + '5' in JavaScript?

• 501

• 105

• 50

• 15

Answer explanation

In JavaScript, when adding a number to a string, the number is converted to a string and concatenated. Therefore, 10 + '5' results in '105'.

What is the purpose of the 'for' loop in JavaScript?

• To iterate over a block of code multiple times

• To change the font color of a webpage

• To calculate complex mathematical equations

• To play music in the background

Answer explanation

The 'for' loop in JavaScript is used to iterate over a block of code multiple times, making it the correct choice.

What is the syntax for the 'switch' statement in JavaScript?

• switch(expression) { case value1: // code block break; case value2: // code block break; ... default: // code block }

• switch(expression) { case value1: // code block break; case value2: // code block break; ... default: // code block}

• switch(expression) { case value1: // code block break; case value2: // code block break; ... default: // code block

• switch{expression} case value1: // code block break; case value2: // code block break; ... default: // code block

Answer explanation

The correct syntax for the 'switch' statement in JavaScript is: switch(expression) { case value1: // code block break; case value2: // code block break; ... default: // code block}

What is the output of the following code: console.log(5 > 3)?

• true

• false

• null

• undefined

Answer explanation

The output of console.log(5 > 3) is 'true' because 5 is greater than 3, which evaluates to true in JavaScript.

How do you declare a constant variable in JavaScript?

• let variableName = value;

• var variableName = value;

• const variableName = value;

• constant variableName = value;

Answer explanation

To declare a constant variable in JavaScript, you use the 'const' keyword followed by the variable name and its value. Therefore, the correct choice is 'const variableName = value;'.

What is the purpose of the 'while' loop in JavaScript?

• To execute a block of code only once

• To skip a block of code

• To repeatedly execute a block of code as long as a specified condition is true.

• To execute a block of code based on a random condition

Answer explanation

To repeatedly execute a block of code as long as a specified condition is true.