Hi, Problem number 1: This form (ps (loop :for i :from 0 :do (print i))) generates: (function () { for (var i = 0; i <= null; i += 1) { print(i); }; })(); I fixed it locally by changing for-from (defun for-from (from-key var state) (unless (atom var) (err "an atom after FROM" var)) (let ((start (eat state)) (op (loop-case from-key (:downfrom '-) (otherwise '+))) (test-op nil) (by nil) (end nil)) (loop while (member (as-keyword (peek state)) '(:to :below :downto :above :by)) do (let ((term (eat state))) (if (eq (as-keyword term) :by) (setf by (eat state)) (setf op (loop-case term ((:downto :above) '-) (otherwise op)) test-op (loop-case term (:to (loop-case from-key (:downfrom '>=) (otherwise '<=))) (:below '<) (:downto '>=) (:above '>)) end (eat state))))) (let ((test (when test-op (list test-op var (maybe-hoist end state))))) (push-iter-clause `(,var ,start (,op ,var ,(or by 1)) ,test) state)))) The difference is that test-op is assigned initially nil, and only re-assigned a value if there is a term. In my example I get infinite loop, but the same behaviour happens if I have more looping constructs, e.g. (loop :for i :from 0 :for j :in list :do (print i)) Problem number 2: Let causes the whole body of loop to be wrapped in function, whereas the previous version wrapped it in with ({ i : i }) { .... } Example: (ps (loop :for i :from 0 :for j :in (array 1 2 3) :do (let ((i i)) (lambda () i)))) generates (function () { var _js207 = [1, 2, 3]; var _js209 = _js207.length; var FIRST210 = true; for (var i = 0; true; i += 1) { (function () { var _js208 = FIRST210 ? 0 : _js208 + 1; if (_js208 >= _js209) { break; }; var j = _js207[_js208]; var i211 = i; function () { return i211; }; return FIRST210 = null; })(); }; })(); The diference is that it is illegal to break from a function body, and it was legal to break from with. Can somebody help please? Cheers, Piotr