Example 1: Convert Decimal to Binary

// program to convert decimal to binary
function convertToBinary(x) {
    let bin = 0;
    let rem, i = 1, step = 1;
    while (x != 0) {
        rem = x % 2;
        console.log(
            `Step ${step++}: ${x}/2, Remainder = ${rem}, Quotient = ${parseInt(x/2)}`
        );
        x = parseInt(x / 2);
        bin = bin + rem * i;
        i = i * 10;
    }
    console.log(`Binary: ${bin}`);
}

// take input
let number = prompt('Enter a decimal number: ');

convertToBinary(number);

Output

Step 1: 9/2, Remainder = 1, Quotient = 4
Step 2: 4/2, Remainder = 0, Quotient = 2
Step 3: 2/2, Remainder = 0, Quotient = 1
Step 4: 1/2, Remainder = 1, Quotient = 0
Binary: 1001

In the above program, the user is prompted to enter a decimal number. The number entered by the user is passed as an argument to the convertToBinary() function.

The while loop is used until the number entered by the user becomes 0.

The binary value is calculated by:

bin = bin + rem * i;

Here, rem is the modulus % value of the number and i gives the place value of the binary number.

Example 2: Convert Decimal to Binary Using toString()

// program to convert decimal to binary

// take input
let number = parseInt(prompt('Enter a decimal number: '));

// convert to binary
let result = number.toString(2);

console.log('Binary:' + ' ' + result);

Output

Enter a decimal number: 9
Binary: 1001

In the above program, the user is prompted to enter a number. The parseInt() method is used to convert a string value to an integer.

The JavaScript built-in method toString([radix]) returns a string value in a specified radix(base). Here, toString(2) converts the decimal number to binary number.