[자바스크립트로 구현한 알고리즘] Return Negative

In this simple assignment you are given a number and have to make it negative. But maybe the number is already negative? 

Example:

makeNegative(1); // return -1 

makeNegative(-5); // return -5 

makeNegative(0); // return 0 

Notes: 

The number can be negative already, in which case no change is required. 

Zero (0) can't be negative, see examples above.