Variadic curried sum function
Not sure if I understood what you want, but
function sum(n) { var v = function(x) { return sum(n + x); }; v.valueOf = v.toString = function() { return n; }; return v;}console.log(+sum(1)(2)(3)(4));
This is an example of using empty brackets in the last call as a close key (from my last interview):
sum(1)(4)(66)(35)(0)()
function sum(numberOne) { var count = numberOne; return function by(numberTwo) { if (numberTwo === undefined) { return count; } else { count += numberTwo; return by; } }}console.log(sum(1)(4)(66)(35)(0)());
I'm posting this revision as its own post since I apparently don't have enough reputation yet to just leave it as a comment. This is a revision of @Rafael 's excellent solution.
function sum (n) { var v = x => sum (n + x); v.valueOf = () => n; return v;}console.log( +sum(1)(2)(3)(4) ); //10I didn't see a reason to keep the v.toString bit, as it didn't seem necessary. If I erred in doing so, please let me know in the comments why v.toString is required (it passed my tests fine without it). Converted the rest of the anonymous functions to arrow functions for ease of reading.