哪些JavaScript函数f满足：f（x，y）= f（a，b）IFF x = a和y = b？

Question

I'm using SlickGrid and the related DataView's groupBy functionality. I would like to group by a pair of columns, but groupBy only allows grouping by a single value.

To get around that (in the AFAICT supported and intended way), I want to pass DataView a function h(row) {return TUPLE(row.x, row.y)} , where TUPLE corresponds to the f in this question's title: it should return an object which behaves with respect to equality as if it was a two-tuple of TUPLE 's first and second argument: [Then DataView would group the rows by h(row) ]

My best solution is something like

x.toString().replace("," by "") + "," + y.toString().replace("," by "")

More generally:

1. Choose a separator string S (eg , )
2. Convert each argument to a string
3. Remove all occurrences of S from each such string
4. Insert S between all the strings (a la return theStrings.join(S) )

My only complaint against this solution is that it feels incredibly icky. That, however, is sufficient to come here and ask if I'm missing some kind of language idiom, best practice or design pattern.

Answer 1

You can use a pairing function if both the two arguments are numbers(or can be converted to numbers).

f(x, y) = (x + y) * (x + y + 1) / 2 + y

See more: http://en.wikipedia.org/wiki/Pairing_function