# Check for Power of two in JavaScript

We are required to write a function, say isPowerOfTwo() that takes in a positive number and returns a boolean based on the fact whether or not the number is some power of 2.

For example −

console.log(isPowerOfTwo(3)); //false
console.log(isPowerOfTwo(32)); //true
console.log(isPowerOfTwo(2048)); //true
console.log(isPowerOfTwo(256)); //true
console.log(isPowerOfTwo(22)); //false

Let’s write the code for this function, it will be a very straightforward recursive function that keeps recurring until the number stays divisible by 2, if in this process the number gets reduced all the way down to 1, it is a power of 2 otherwise it isn’t. Here is the code −

## Example

const isPowerOfTwo = num => {
if(num === 1){
return true;
};
if(num % 2 !== 0){
return false;
}
return isPowerOfTwo(num / 2);
}
console.log(isPowerOfTwo(3));
console.log(isPowerOfTwo(32));
console.log(isPowerOfTwo(2048));
console.log(isPowerOfTwo(256));
console.log(isPowerOfTwo(22));

## Output

The output in the console will be −

false
true
true
true
false

Updated on: 26-Aug-2020

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