JavaScript Program to Check Voting Eligibility

Use a simple JavaScript program like if (age >= 18) { console.log('Eligible to vote'); } else { console.log('Not eligible to vote'); } to check if a person is old enough to vote.

Examples

Input17

OutputNot eligible to vote

Input18

OutputEligible to vote

Input25

OutputEligible to vote

How to Think About It

To check voting eligibility, first get the person's age. Then compare the age with the minimum voting age, which is 18. If the age is 18 or more, the person can vote; otherwise, they cannot.

Algorithm

1

Get the person's age as input.

2

Check if the age is greater than or equal to 18.

3

If yes, print 'Eligible to vote'.

4

If no, print 'Not eligible to vote'.

Code

javascript

const age = 20;
if (age >= 18) {
  console.log('Eligible to vote');
} else {
  console.log('Not eligible to vote');
}

Output

Eligible to vote

Dry Run

Let's trace the program with age = 20 through the code

1

Set age

age = 20

2

Check age >= 18

20 >= 18 is true

3

Print result

Print 'Eligible to vote'

age	age >= 18	output
20	true	Eligible to vote

Why This Works

Step 1: Compare age with 18

The code uses age >= 18 to check if the person is old enough to vote.

Step 2: Print eligibility

If the condition is true, it prints 'Eligible to vote', otherwise 'Not eligible to vote'.

Alternative Approaches

Using a function

javascript

function checkVotingEligibility(age) {
  return age >= 18 ? 'Eligible to vote' : 'Not eligible to vote';
}
console.log(checkVotingEligibility(16));

This approach makes the code reusable for different ages.

Using prompt for input

javascript

const age = parseInt(prompt('Enter your age:'), 10);
if (age >= 18) {
  console.log('Eligible to vote');
} else {
  console.log('Not eligible to vote');
}

This allows user input in a browser environment.

Complexity: O(1) time, O(1) space

Time Complexity

The program performs a single comparison operation, so it runs in constant time.

Space Complexity

It uses a fixed amount of memory for the age variable and output, so constant space.

Which Approach is Fastest?

All approaches run in constant time and space; using a function adds reusability but no performance cost.

Approach	Time	Space	Best For
Simple if-else	O(1)	O(1)	Quick checks
Function with ternary	O(1)	O(1)	Reusable code
Prompt input	O(1)	O(1)	Interactive user input