functional programming rules.txt

1. Don't alter a variable or object - create new variables and objects and return them if need be from a function. Hint: using something like var newArr = arrVar, where arrVar is an array will simply create a reference to the existing variable and not a copy. So changing a value in newArr would change the value in arrVar.

2. Declare function parameters - any computation inside a function depends only on the arguments passed to the function, and not on any global object or variable.