Pure functions The ideal in functional programming is what is known as pure functions. A pure function is one whose results are dependent only upon the input parameters, and whose operation ...

This detailed tutorial shows how to implement pure functions in JavaScript that are deterministic and referentially transparent, and create no side effects.

Code examples in these sections will get you started with pure functions, higher-order functions, lazy evaluation, closures, and currying. Functional programming is on the rise ...

With example-based testing, the expected output of the function under test can be computed ahead of time and compared to the actual output of the function.

For example, in a call to List.map, the overall expression is pure if the function argument to List.map is pure. We say that such functions are considered effect polymorphic.