# Decimal to binary conversion using recursion in JavaScript

We are required to write a JavaScript function that takes in a number as the first and the only argument. The function should use recursion to construct a string representing the binary notation of that number.

For example −

f(4) = '100'
f(1000) = '1111101000'
f(8) = '1000'

## Example

Following is the code −

const decimalToBinary = (num) => {
if(num >= 1) {
// If num is not divisible by 2 then recursively return proceeding
// binary of the num minus 1, 1 is added for the leftover 1 num
if (num % 2) {
return decimalToBinary((num - 1) / 2) + 1;
} else {
// Recursively return proceeding binary digits
return decimalToBinary(num / 2) + 0;
}
} else {
// Exit condition
return '';
};
};
console.log(decimalToBinary(4));
console.log(decimalToBinary(1000));
console.log(decimalToBinary(8));

## Output

Following is the output on console −

100
1111101000
1000

Updated on: 10-Dec-2020

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