Make the syntax work sum(1)(2)(3).......(n) [Asked in multiple interviews]

sum-curry-arity.js

function sum(a) {
	var resp = a;
	function innerSum(b) {
		resp += b;
		return innerSum;
	}
	innerSum.toString = function(){
		return resp;
	}
	return innerSum;
}

sum(1)(2)(3)(4)(5);