diff --git a/jsbuiltin.c b/jsbuiltin.c
index ddc2ec5..25c8166 100644
--- a/jsbuiltin.c
+++ b/jsbuiltin.c
@@ -94,6 +94,35 @@ static void jsB_initstring(js_State *J)
 	js_setglobal(J, "String");
 }
 
+static int jsB_parseInt(js_State *J, int argc)
+{
+	const char *s = js_tostring(J, 1);
+	double radix = argc > 1 ? js_tonumber(J, 2) : 10;
+	js_pushnumber(J, strtol(s, NULL, radix == 0 ? 10 : radix));
+	return 1;
+}
+
+static int jsB_parseFloat(js_State *J, int argc)
+{
+	const char *s = js_tostring(J, 1);
+	js_pushnumber(J, strtod(s, NULL));
+	return 1;
+}
+
+static int jsB_isNaN(js_State *J, int argc)
+{
+	double n = js_tonumber(J, 1);
+	js_pushboolean(J, isnan(n));
+	return 1;
+}
+
+static int jsB_isFinite(js_State *J, int argc)
+{
+	double n = js_tonumber(J, 1);
+	js_pushboolean(J, isfinite(n));
+	return 1;
+}
+
 static void jsB_register(js_State *J, const char *name, js_CFunction cfun)
 {
 	js_pushcfunction(J, cfun);
@@ -109,6 +138,20 @@ void jsB_init(js_State *J)
 	jsB_initnumber(J);
 	jsB_initstring(J);
 
+	js_pushnumber(J, NAN);
+	js_setglobal(J, "NaN");
+
+	js_pushnumber(J, INFINITY);
+	js_setglobal(J, "Infinity");
+
+	js_pushundefined(J);
+	js_setglobal(J, "undefined");
+
 	jsB_register(J, "eval", jsB_eval);
+	jsB_register(J, "parseInt", jsB_parseInt);
+	jsB_register(J, "parseFloat", jsB_parseFloat);
+	jsB_register(J, "isNaN", jsB_isNaN);
+	jsB_register(J, "isFinite", jsB_isFinite);
+
 	jsB_register(J, "print", jsB_print);
 }
diff --git a/jsrun.h b/jsrun.h
index 71e3b13..063f06b 100644
--- a/jsrun.h
+++ b/jsrun.h
@@ -7,10 +7,14 @@ struct js_Environment
 	js_Object *variables;
 };
 
+/* private */
 void jsB_init(js_State *J);
 js_Environment *jsR_newenvironment(js_State *J, js_Object *variables, js_Environment *outer);
 int jsR_loadscript(js_State *J, const char *filename, const char *source);
 void jsR_error(js_State *J, const char *fmt, ...);
+void js_pushobject(js_State *J, js_Object *v);
+
+/* public */
 
 void js_call(js_State *J, int n);