Prime Factors

Compute the prime factors of a given natural number.

A prime number is only evenly divisible by itself and 1.

Note that 1 is not a prime number.

Example

What are the prime factors of 60?

Our first divisor is 2. 2 goes into 60, leaving 30.
2 goes into 30, leaving 15.
- 2 doesn't go cleanly into 15. So let's move on to our next divisor, 3.
3 goes cleanly into 15, leaving 5.
- 3 does not go cleanly into 5. The next possible factor is 4.
- 4 does not go cleanly into 5. The next possible factor is 5.
5 does go cleanly into 5.
We're left only with 1, so now, we're done.

Our successful divisors in that computation represent the list of prime factors of 60: 2, 2, 3, and 5.

You can check this yourself:

Go through the setup instructions for JavaScript to install the necessary dependencies:

Execute the tests with:

$ jasmine-node .

In many test suites all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by changing xit to it.

The Prime Factors Kata by Uncle Bob view source