Unary operators in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to increase the value of count by 1 using a unary operator.

Javascript

let count = 5;
count[1];
console.log(count);

Drag options to blanks, or click blank then click option'

A-

B++

C+=

D--

Attempts:

3 left

💡 Hint

Common Mistakes

Using '--' which decreases the value.

Using '+=' which is not a unary operator.

Using '-' which subtracts but is not unary increment.

The unary increment operator ++ increases the value by 1.

2fill in blank

medium

Complete the code to convert the string numStr to a number using a unary operator.

Javascript

let numStr = "42";
let num = [1]numStr;
console.log(typeof num);

Drag options to blanks, or click blank then click option'

A+

BNumber

CparseInt

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using parseInt which is a function, not a unary operator.

Using Number which is a function, not a unary operator.

Using '-' which negates the number but does not convert string to number.

The unary plus operator converts a string to a number.

3fill in blank

hard

Fix the error in the code by choosing the correct unary operator to negate the value of value.

Javascript

let value = 10;
let negated = [1]value;
console.log(negated);

Drag options to blanks, or click blank then click option'

A-

B+

C++

D--

Attempts:

3 left

💡 Hint

Common Mistakes

Using '++' which increments the value.

Using '+' which does not change the sign.

Using '--' which decrements the value.

The unary minus operator negates the value, turning 10 into -10.

4fill in blank

hard

Fill both blanks to create an object flags where keys are numbers and values are their negations using unary operators.

Javascript

const numbers = [1, 2, 3];
const flags = {};
for (const num of numbers) {
  flags[[1]] = [2];
}
console.log(flags);

Drag options to blanks, or click blank then click option'

Anum

B-num

Cnum.toString()

Dnum * -1

Attempts:

3 left

💡 Hint

Common Mistakes

Using number directly as key without converting to string.

Using multiplication instead of unary minus for negation.

Using 'num' as value which is not negated.

Keys must be strings, so num.toString() is used. Values are negated with unary minus -num.

5fill in blank

hard

Fill both blanks to create a new array results where each element is the negation of the numeric conversion of strings in arr.

Javascript

const arr = ["5", "-3", "10"];
const results = arr.map(item => [1][2]item);
console.log(results);

Drag options to blanks, or click blank then click option'

A-

B+

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using logical NOT ! which converts to boolean.

Not converting string to number before negation.

Placing operators incorrectly causing syntax errors.

First, unary plus + converts string to number, then unary minus - negates it. The empty string '' is used to separate operators correctly.