JavaScript Course | Practice Quiz-2

Question 1

Which of the following javascript functions allows you to get user input data?

• A. alert
• B. prompt
• C. confirm
• D. None of the above

Answer: (B)

JavaScript Course Quiz 2
Discuss it

Only prompt creates an input field where the user can enter the data.

Question 2

Which logical operator only accepts a single operand?

• A. &&(AND)
• B. ||(OR)
• C. !(NOT)
• D. None of the above

Answer: (C)

JavaScript Course Quiz 2
Discuss it

Only the !(NOT) operator takes a single operand. It flips the value.

Question 3

What will be the result of the following code?

<script>
  document.write( true && 1 && 3);
</script>

• A. 0
• B. 1
• C. true
• D. 3

Answer: (D)

JavaScript Course Quiz 2
Discuss it

The && (and operator) returns the last (right-side) value as long as the chain is "truthy" or True.

Question 4

What will be the output of the following code?

 <script>
   document.write((0 && 1) || (1 || 0));
 </script>

• A. 0
• B. false
• C. true
• D. 1

Answer: (D)

JavaScript Course Quiz 2
Discuss it

The && (and operator) returns the last (right-side) value as long as the chain is "truthy". The || (or operator) returns true if either of the value is true.

Question 5

What will be the output of the following code?

<script>
 let ans = 0 / 0;
 document.write(ans);
</script>

• A. 0
• B. infinity
• C. NaN
• D. None of the above

Answer: (C)

JavaScript Course Quiz 2
Discuss it

0/0 is undefined for the real number and is therefore represented by NaN (Not a Number) in Javascript.

Question 6

What will be the output of the following code?

<script>
 let i = 30;
  if( i == 10 || i > 20){
    console.log('Hola');
  }else if( i == 5){
    console.log('Breaking up the code');
  }else{
    console.log('Adios');
 }
</script>

• A. Hola
• B. Breaking up the code
• C. Adios
• D. None of the above

Answer: (A)

JavaScript Course Quiz 2
Discuss it

The if() statement will be executed if the condition in the bracket returns true otherwise the else statement is executed.

Question 7

What will be the output of the following code?

 <script>
   let ans = 1;
   document.write( ans === '1');
 </script>

• A. true
• B. false
• C. 0
• D. None of the above

Answer: (B)

JavaScript Course Quiz 2
Discuss it

The strict equality operator compares both the value and the type of the operands.

Question 8

What will be the output of the following code?

 <script>
  let age = 20;
  let result = age>18 ? 'Great' : 'Not so great';
  document.write(result);
 </script>

• A. Great
• B. Not so great
• C. true
• D. None of the above

Answer: (A)

JavaScript Course Quiz 2
Discuss it

?: is a ternary operator which will return the value after '?' if true else it will return the value after ':'.

Question 9

What will be the output of the following code?

<script>
  let y = 1;
  y = typeof x; 
  document.write(typeof y);
</script>

• A. string
• B. null
• C. number
• D. boolean

Answer: (A)

JavaScript Course Quiz 2
Discuss it

typeof 'undefined' is a string and if we do typeof 'string' again it will be the same.

Question 10

What will be the output of the following code?

 <script>
    var x = [typeof x, typeof y][1];
    document.write(typeof typeof x);
 </script>

• A. undefined
• B. string
• C. number
• D. boolean

Answer: (B)

JavaScript Course Quiz 2
Discuss it

typeof 'y' which is undefined returns 'undefined', typeof 'undefined' is 'string', and another typeof on it still returns 'string'.