var O = toObject(source);
var argumentsLength = arguments.length;
var mapfn = argumentsLength > 1 ? arguments[1] : undefined;
var mapping = mapfn !== undefined;
var iteratorMethod = getIteratorMethod(O);
var i, length, result, step, iterator, next;
var O = toObject(source);
var argumentsLength = arguments.length;
var mapfn = argumentsLength > 1 ? arguments[1] : undefined;
var mapping = mapfn !== undefined;
var iteratorMethod = getIteratorMethod(O);
var i, length, result, step, iterator, next;