Get if array item has complement

find_complement.js

var hasComplement = function (array, sum) {
	if (sum < 0)
		throw "sum must be bigger than 0";

	var complements = [];

	for (var i = 0, complement; i < array.length; i++, complement = sum - array[i]) { 	
		if (array.indexOf(complement) != -1) // if (complement.indexOf(array[i]) != -1)
			return true;
		else
			complements.push(complement);
    }
	
	return false;
};

var notFoundable = [1,9,3,2],
	foundable = [1,4,2,4],
	charles = [4,3,5,1];

hasComplement(notFoundable, 8);
hasComplement(foundable, 8);
hasComplement(charles, 8);