diff --git a/README.md b/README.md
index c34f5a3..ca56e56 100644
--- a/README.md
+++ b/README.md
@@ -239,32 +239,24 @@ char *js_getstr(struct js *js, jsval_t val, size_t *len);  // Get string
 
 Extract C values from JS values
 
-### js\_checkargs()
+### js\_chkargs()
 
 ```c
-jsval_t js_checkargs(struct js *js, jsval_t *args, int nargs, const char *spec, ...);
+bool js_chkargs(jsval_t *args, int nargs, const char *spec);
 ```
 
-A helper function that fetches JS arguments into C values, according to
-`spec` type specification. Return `JS_ERR` on error, or `JS_UNDEF` on success.
-Supported specifiers:
-- `b` for `bool`
-- `d` for `double`
-- `i` for `char`, `short`, `int`, and corresponding unsigned variants
-- `s` for `char *`
-- `j` for `jsval_t`
+A helper function that checks a validity of the arguments passed to a function.
+A `spec` is a 0-terminated string where each character represents a type of
+the expected argument: `b` for `bool`, `d` for number, `s` for string, `j`
+for any other JS value.
 
 Usage example - a C function that implements a JS function
 `greater_than(number1, number2)`:
 
 ```c
-jsval_t js_gt(struct js *js, jsval_t *args, int nargs) {
-  double a, b;
-  jsval_t res = js_checkargs(js, args, nargs, "dd", &a, &b);
-  if (js_type(res) == JS_UNDEF) {
-    res = a > b ? js_mktrue() : js_mkfalse();
-  }
-  return res;
+static jsval_t js_gt(struct js *js, jsval_t *args, int nargs) {
+  if (!js_chkargs(args, nargs, "dd")) return js_mkerr(js, "bad args!");
+  return js_getnum(args[0]) > js_getnum(args[1]) ? js_mktrue() : js_mkfalse();
 }
 ```
 
diff --git a/elk.c b/elk.c
index 94dd348..9f629a8 100644
--- a/elk.c
+++ b/elk.c
@@ -21,10 +21,8 @@
 #endif
 
 #include <assert.h>
-#include <inttypes.h>
 #include <math.h>
 #include <stdarg.h>
-#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -866,14 +864,20 @@ static jsval_t js_obj_literal(struct js *js) {
   if (is_err(obj)) return obj;
   js->consumed = 1;
   while (next(js) != TOK_RBRACE) {
-    EXPECT(TOK_IDENTIFIER, );
-    size_t koff = js->toff, klen = js->tlen;
+    jsval_t key = 0;
+    if (js->tok == TOK_IDENTIFIER) {
+      if (exe) key = js_mkstr(js, js->code + js->toff, js->tlen);
+    } else if (js->tok == TOK_STRING) {
+      if (exe) key = js_str_literal(js);
+    } else {
+      return js_mkerr(js, "parse error");
+    }
+    js->consumed = 1;
     EXPECT(TOK_COLON, );
     jsval_t val = js_expr(js);
     if (exe) {
       // printf("XXXX [%s] scope: %lu\n", js_str(js, val), vdata(js->scope));
       if (is_err(val)) return val;
-      jsval_t key = js_mkstr(js, js->code + koff, klen);
       if (is_err(key)) return key;
       jsval_t res = setprop(js, obj, key, resolveprop(js, val));
       if (is_err(res)) return res;
@@ -1369,27 +1373,15 @@ void js_stats(struct js *js, size_t *total, size_t *lwm, size_t *css) {
 }
 // clang-format on
 
-jsval_t js_checkargs(struct js *js, jsval_t *args, int nargs, const char *spec,
-                     ...) {
-  va_list ap;
-  int i = 0;
-  va_start(ap, spec);
-  for (i = 0; i < nargs; i++) {
-    uint8_t t = vtype(args[i]);
-    switch (spec[i]) {  // clang-format off
-      case 'b': if (t != T_BOOL) goto fail; *(va_arg(ap, bool *)) = js_getbool(args[i]); break;
-      case 'd': if (t != T_NUM) goto fail; *(va_arg(ap, double *)) = js_getnum(args[i]); break;
-      case 'i': if (t != T_NUM) goto fail; *(va_arg(ap, int *)) = (int) js_getnum(args[i]); break;
-      case 's': if (t != T_STR) goto fail; *(va_arg(ap, char **)) = js_getstr(js, args[i], NULL); break;
-      case 'j': *(va_arg(ap, jsval_t *)) = args[i]; break;
-      default: goto fail;
-    }  // clang-format on
+bool js_chkargs(jsval_t *args, int nargs, const char *spec) {
+  int i = 0, ok = 1;
+  for (; ok && i < nargs && spec[i]; i++) {
+    uint8_t t = vtype(args[i]), c = (uint8_t) spec[i];
+    ok = (c == 'b' && t == T_BOOL) || (c == 'd' && t == T_NUM) ||
+         (c == 's' && t == T_STR) || (c == 'j');
   }
-  va_end(ap);
-  if (spec[i] != '\0') return js_mkerr(js, "arg count");
-  return js_mkundef();
-fail:
-  return js_mkerr(js, "arg %d", i);
+  if (spec[i] != '\0' || i != nargs) ok = 0;
+  return ok;
 }
 
 jsval_t js_eval(struct js *js, const char *buf, size_t len) {
diff --git a/elk.h b/elk.h
index edb7875..711634a 100644
--- a/elk.h
+++ b/elk.h
@@ -17,6 +17,7 @@
 #define JS_VERSION "3.0.0"
 #pragma once
 
+#include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ -31,9 +32,9 @@ struct js *js_create(void *buf, size_t len);         // Create JS instance
 jsval_t js_eval(struct js *, const char *, size_t);  // Execute JS code
 jsval_t js_glob(struct js *);                        // Return global object
 const char *js_str(struct js *, jsval_t val);        // Stringify JS value
-jsval_t js_checkargs(struct js *, jsval_t *, int, const char *, ...);  // Check
-void js_setmaxcss(struct js *, size_t);  // Set max C stack size
-void js_setgct(struct js *, size_t);     // Set GC trigger threshold
+bool js_chkargs(jsval_t *, int, const char *);       // Check args validity
+void js_setmaxcss(struct js *, size_t);              // Set max C stack size
+void js_setgct(struct js *, size_t);                 // Set GC trigger threshold
 void js_stats(struct js *, size_t *total, size_t *min, size_t *cstacksize);
 void js_dump(struct js *);  // Print debug info. Requires -DJS_DUMP
 
diff --git a/examples/Esp32JS/JS.h b/examples/Esp32JS/JS.h
index 1effbf9..23a6270 100644
--- a/examples/Esp32JS/JS.h
+++ b/examples/Esp32JS/JS.h
@@ -55,33 +55,26 @@ static void logstats(void) {
 // These functions below will be imported into the JS engine.
 // Note that they are inside the extern "C" section.
 static jsval_t gpio_write(struct js *js, jsval_t *args, int nargs) {
-  int pin, val;
-  jsval_t res = js_checkargs(js, args, nargs, "ii", &pin, &val);
-  if (js_type(res) == JS_UNDEF) {
-    MG_INFO(("gpio.write %d -> %d", pin, val));
-    digitalWrite(pin, val);
-  }
-  return res;
+  if (!js_chkargs(args, nargs, "dd")) return js_mkerr(js, "bad args");
+  int pin = js_getnum(args[0]), val = js_getnum(args[1]);
+  MG_INFO(("gpio.write %d -> %d", pin, val));
+  digitalWrite(pin, val);
+  return js_mknull();
 }
 
 static jsval_t gpio_read(struct js *js, jsval_t *args, int nargs) {
-  int pin;
-  jsval_t res = js_checkargs(js, args, nargs, "i", &pin);
-  if (js_type(res) == JS_UNDEF) {
-    MG_INFO(("gpio.read %d", pin));
-    res = js_mknum(digitalRead(pin));
-  }
-  return res;
+  if (!js_chkargs(args, nargs, "d")) return js_mkerr(js, "bad args");
+  int pin = js_getnum(args[0]);
+  MG_INFO(("gpio.read %d", pin));
+  return js_mknum(digitalRead(pin));
 }
 
 static jsval_t gpio_mode(struct js *js, jsval_t *args, int nargs) {
-  int pin, mode;
-  jsval_t res = js_checkargs(js, args, nargs, "ii", &pin, &mode);
-  if (js_type(res) == JS_UNDEF) {
-    MG_INFO(("gpio.mode %d -> %d", pin, mode));
-    pinMode(pin, mode);
-  }
-  return res;
+  if (!js_chkargs(args, nargs, "dd")) return js_mkerr(js, "bad args");
+  int pin = js_getnum(args[0]), mode = js_getnum(args[1]);
+  MG_INFO(("gpio.mode %d -> %d", pin, mode));
+  pinMode(pin, mode);
+  return js_mknull();
 }
 
 void timer_cleanup(void *data) {
@@ -105,26 +98,20 @@ static void js_timer_fn(void *userdata) {
 }
 
 static jsval_t mktimer(struct js *js, jsval_t *args, int nargs) {
-  int milliseconds = 0;
-  const char *funcname = NULL;
-  jsval_t res = js_checkargs(js, args, nargs, "is", &milliseconds, &funcname);
-  if (js_type(res) == JS_UNDEF) {
-    struct mg_timer *t = mg_timer_add(&s_mgr, milliseconds, MG_TIMER_REPEAT,
-                                      js_timer_fn, strdup(funcname));
-    MG_INFO(("mktimer %lu, %d ms, fn %s", t->id, milliseconds, funcname));
-    addresource(timer_cleanup, (void *) t->id);
-    res = js_mknum(t->id);
-  }
-  return res;
+  if (!js_chkargs(args, nargs, "ds")) return js_mkerr(js, "bad args");
+  int milliseconds = js_getnum(args[0]);
+  const char *funcname = js_getstr(js, args[1], NULL);
+  struct mg_timer *t = mg_timer_add(&s_mgr, milliseconds, MG_TIMER_REPEAT,
+                                    js_timer_fn, strdup(funcname));
+  MG_INFO(("mktimer %lu, %d ms, fn %s", t->id, milliseconds, funcname));
+  addresource(timer_cleanup, (void *) t->id);
+  return js_mknum(t->id);
 }
 
 static jsval_t deltimer(struct js *js, jsval_t *args, int nargs) {
-  unsigned long id;
-  jsval_t res = js_checkargs(js, args, nargs, "i", &id);
-  if (js_type(res) == JS_UNDEF) {
-    delresource(timer_cleanup, (void *) id);
-  }
-  return res;
+  if (!js_chkargs(args, nargs, "d")) return js_mkerr(js, "bad args");
+  delresource(timer_cleanup, (void *) (unsigned long) js_getnum(args[0]));
+  return js_mknull();
 }
 
 static jsval_t js_log(struct js *js, jsval_t *args, int nargs) {
diff --git a/test/unit_test.c b/test/unit_test.c
index 507e2c7..cbbd743 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -126,6 +126,8 @@ static void test_basic(void) {
   assert(ev(js, "a = {b:2}", "{\"b\":2}"));
   assert(ev(js, "a", "{\"b\":2}"));
   assert(ev(js, "a.b", "2"));
+  assert(ev(js, "({a:3}).a", "3"));
+  assert(ev(js, "({\"a\":4})", "{\"a\":4}"));
   assert(ev(js, "a.b = {c:3}", "{\"c\":3}"));
   assert(ev(js, "a", "{\"b\":{\"c\":3}}"));
   assert(ev(js, "a.b.c", "3"));
@@ -419,6 +421,12 @@ static void test_funcs(void) {
   assert(ev(js, "f() + 2;", "3"));
 
   assert(ev(js, "f=function (x){return x+1;}; f(1);", "2"));
+
+  assert(ev(js, "f = function(x){return x;};", "function(x){return x;}"));
+  assert(ev(js, "f(2)", "2"));
+  assert(ev(js, "f({})", "{}"));
+  assert(ev(js, "f({a:5,b:3}).b", "3"));
+  assert(ev(js, "f({\"a\":5,\"b\":3}).b", "3"));
 }
 
 static void test_bool(void) {
@@ -516,12 +524,8 @@ static jsval_t js_set_timer(struct js *js, jsval_t *args, int nargs) {
 }
 
 static jsval_t js_gt(struct js *js, jsval_t *args, int nargs) {
-  double a, b;
-  jsval_t res = js_checkargs(js, args, nargs, "dd", &a, &b);
-  if (js_type(res) == JS_UNDEF) {
-    res = a > b ? js_mktrue() : js_mkfalse();
-  }
-  return res;
+  if (!js_chkargs(args, nargs, "dd")) return js_mkerr(js, "doh");
+  return js_getnum(args[0]) > js_getnum(args[1]) ? js_mktrue() : js_mkfalse();
 }
 
 static void test_c_funcs(void) {
@@ -530,9 +534,9 @@ static void test_c_funcs(void) {
 
   assert((js = js_create(mem, sizeof(mem))) != NULL);
   js_set(js, js_glob(js), "gt", js_mkfun(js_gt));
-  assert(ev(js, "gt()", "ERROR: arg count"));
-  assert(ev(js, "gt(1,null)", "ERROR: arg 1"));
-  assert(ev(js, "gt(null, 1)", "ERROR: arg 0"));
+  assert(ev(js, "gt()", "ERROR: doh"));
+  assert(ev(js, "gt(1,null)", "ERROR: doh"));
+  assert(ev(js, "gt(null, 1)", "ERROR: doh"));
   assert(ev(js, "gt(1,2)", "false"));
   assert(ev(js, "gt(1,1)", "false"));
   assert(ev(js, "gt(2,1)", "true"));
@@ -547,6 +551,15 @@ static void test_c_funcs(void) {
   if (s_timer_fn) s_timer_fn(1, s_timer_fn_data);  // C code calls timer
   assert(ev(js, "v", "8"));
   // printf("--> [%s]\n", js_str(js, js_glob(js)));
+
+  jsval_t args[] = {0, js_mktrue(), js_mkstr(js, "a", 1), js_mknull()};
+  assert(js_chkargs(args, 4, "dbsj") == true);
+  assert(js_chkargs(args, 4, "dbsjb") == false);
+  assert(js_chkargs(args, 4, "bbsj") == false);
+  assert(js_chkargs(args, 4, "ddsj") == false);
+  assert(js_chkargs(args, 4, "dbdj") == false);
+  assert(js_chkargs(args, 4, "dbss") == false);
+  assert(js_chkargs(args, 4, "d") == false);
 }
 
 static void test_ternary(void) {