Is power of two is an algorithm to determine if a number is a power of 2. Learn how to implement it in JavaScript.

Given a positive integer, write a function to find if it is a power of two or not.

**Naive solution**

In naive solution we just keep dividing the number by two unless the number becomes 1 and every time we do so, we check that remainder after division is always 0. Otherwise, the number can't be a power of two.

**Bitwise solution**

Powers of two in binary form always have just one bit set. The only exception is with a signed integer (e.g. an 8-bit signed integer with a value of -128 looks like: 10000000)

```
1: 0001
2: 0010
4: 0100
8: 1000
```

So after checking that the number is greater than zero, we can use a bitwise hack to test that one and only one bit is set.

```
number & (number - 1)
```

For example for number 8 that operations will look like:

```
1000
- 0001
----
0111
1000
& 0111
----
0000
```

**The ****Original Article**** can be found on https://github.com**

#javascript #algorithms #datastructures #math

3.65 GEEK