Mastering JavaScript Functional Programming - Second Edition

More complex memoization

What can we do if we have to work with a function that receives two or more arguments, or that can receive arrays or objects as arguments? Of course, like in the problem that we looked at in Chapter 2, Thinking Functionally – A First Example, about having a function do its job only once, we could simply ignore the question: if the function to be memoized is unary, we go through the memoization process; otherwise, if the function has a different arity, we just don't do anything!

The number of parameters of a function is called the arity of the function, or its valence. You may speak in three different ways: you can say a function has arity 1, 2, 3, and so on; you can say that a function is unary, binary, ternary, and ...