A Program to Check if a Number is Odd or Even

In this JavaScript lesson, we will practice how to write a program to check if a number is odd or even using a condition/decision-making statement and ternary operator.

Practice A: Check Even or Odd Number using if-else Condition

// Request user to insert a number

const num = prompt("Enter any number: ");
//check for even numberif(num % 2 == 0) 
{   
 console.log("This is an even number.");
} 
// check for odd number
else {    
console.log("This is an odd number.");
}

Output

Enter any number: 9

This is an odd number.

The program was executed successfully with the help of the condition statement, num % 2 == 0. This statement checks if the number entered by the user is even, odd, or zero. When the remainder = 0, the number entered is an even number. Else the number is an odd number.

Even numbers are numbers that are divisible by 2 without remainder or remainder = 0.

The modulus operator % returns only the remainder when used with a number. See the example below,

const num = 8;
const output = num % 2; 

// remainder is 0

Note that when % is used with 2 and the remainder is equal to zero (0), the number is an even number. Else, the number is an odd number.

Practice B: Check Even or Odd Number using Ternary Operator

The ternary operator is a JavaScript operator which takes three operands rather than the typical one or two that most operators use. It provides a way to shorten a simple if-else block in JavaScript programs. Let’s quickly look at the example below.

// Request input from user
const num = prompt("Enter any number: ");

// apply ternary operator
const output = (num % 2  == 0) ? "even" : "odd";

// display result on console
console.log(`This is an ${output} number.`);

Output

Enter any number: 7

This is an odd number.

Ternary operators make JavaScript statements more concise, shortened, and easy to use. This is also applicable in other programming languages. As a beginner, the syntax may be new to you and the operator may seem a little confusing at the moment. Play more with it and you will get better as you go on writing JavaScript programs.

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