8 files changed, 36 insertions, 10 deletions
diff --git a/platform/javascript/.eslintrc.libs.js b/platform/javascript/.eslintrc.libs.js
index e5f0c3d147..81b1b8c864 100644
--- a/platform/javascript/.eslintrc.libs.js
+++ b/platform/javascript/.eslintrc.libs.js
@@ -18,5 +18,8 @@ module.exports = {
 		"GodotRuntime": true,
 		"GodotFS": true,
 		"IDHandler": true,
+		"Browser": true,
+		"GL": true,
+		"XRWebGLLayer": true,
 	},
 };
diff --git a/platform/javascript/SCsub b/platform/javascript/SCsub
index 7a8005fe30..b0302a5f88 100644
--- a/platform/javascript/SCsub
+++ b/platform/javascript/SCsub
@@ -27,8 +27,13 @@ if env["tools"]:
     sys_env.AddJSLibraries(["js/libs/library_godot_editor_tools.js"])
 if env["javascript_eval"]:
     sys_env.AddJSLibraries(["js/libs/library_godot_eval.js"])
+
 for lib in sys_env["JS_LIBS"]:
     sys_env.Append(LINKFLAGS=["--js-library", lib])
+for js in env["JS_PRE"]:
+    sys_env.Append(LINKFLAGS=["--pre-js", env.File(js).path])
+for ext in env["JS_EXTERNS"]:
+    sys_env["ENV"]["EMCC_CLOSURE_ARGS"] += " --externs " + ext.path
 
 build = []
 if env["gdnative_enabled"]:
@@ -66,6 +71,8 @@ else:
     build = sys_env.Program(build_targets, javascript_files + ["javascript_runtime.cpp"])
 
 sys_env.Depends(build[0], sys_env["JS_LIBS"])
+sys_env.Depends(build[0], sys_env["JS_PRE"])
+sys_env.Depends(build[0], sys_env["JS_EXTERNS"])
 
 engine = [
     "js/engine/preloader.js",
diff --git a/platform/javascript/detect.py b/platform/javascript/detect.py
index d53c774e77..0d57f8aad1 100644
--- a/platform/javascript/detect.py
+++ b/platform/javascript/detect.py
@@ -1,7 +1,7 @@
 import os
 import sys
 
-from emscripten_helpers import run_closure_compiler, create_engine_file, add_js_libraries
+from emscripten_helpers import run_closure_compiler, create_engine_file, add_js_libraries, add_js_pre, add_js_externs
 from methods import get_compiler_version
 from SCons.Util import WhereIs
 
@@ -131,8 +131,13 @@ def configure(env):
         jscc = env.Builder(generator=run_closure_compiler, suffix=".cc.js", src_suffix=".js")
         env.Append(BUILDERS={"BuildJS": jscc})
 
-    # Add helper method for adding libraries.
+    # Add helper method for adding libraries, externs, pre-js.
+    env["JS_LIBS"] = []
+    env["JS_PRE"] = []
+    env["JS_EXTERNS"] = []
     env.AddMethod(add_js_libraries, "AddJSLibraries")
+    env.AddMethod(add_js_pre, "AddJSPre")
+    env.AddMethod(add_js_externs, "AddJSExterns")
 
     # Add method that joins/compiles our Engine files.
     env.AddMethod(create_engine_file, "CreateEngineFile")
diff --git a/platform/javascript/emscripten_helpers.py b/platform/javascript/emscripten_helpers.py
index cc874c432e..8b8c492e22 100644
--- a/platform/javascript/emscripten_helpers.py
+++ b/platform/javascript/emscripten_helpers.py
@@ -22,6 +22,12 @@ def create_engine_file(env, target, source, externs):
 
 
 def add_js_libraries(env, libraries):
-    if "JS_LIBS" not in env:
-        env["JS_LIBS"] = []
     env.Append(JS_LIBS=env.File(libraries))
+
+
+def add_js_pre(env, js_pre):
+    env.Append(JS_PRE=env.File(js_pre))
+
+
+def add_js_externs(env, externs):
+    env.Append(JS_EXTERNS=env.File(externs))
diff --git a/platform/javascript/http_client_javascript.cpp b/platform/javascript/http_client_javascript.cpp
index 44819c495c..c8c48dd582 100644
--- a/platform/javascript/http_client_javascript.cpp
+++ b/platform/javascript/http_client_javascript.cpp
@@ -220,13 +220,13 @@ Error HTTPClient::poll() {
 				has_polled = true;
 			} else {
 				// forcing synchronous requests is not possible on the web
-				if (last_polling_frame == Engine::get_singleton()->get_idle_frames()) {
+				if (last_polling_frame == Engine::get_singleton()->get_process_frames()) {
 					WARN_PRINT("HTTPClient polled multiple times in one frame, "
 							   "but request cannot progress more than once per "
 							   "frame on the HTML5 platform.");
 				}
 			}
-			last_polling_frame = Engine::get_singleton()->get_idle_frames();
+			last_polling_frame = Engine::get_singleton()->get_process_frames();
 #endif
 
 			polled_response_code = godot_xhr_get_status(xhr_id);
diff --git a/platform/javascript/javascript_main.cpp b/platform/javascript/javascript_main.cpp
index 5656ecd7dc..0b8af70b13 100644
--- a/platform/javascript/javascript_main.cpp
+++ b/platform/javascript/javascript_main.cpp
@@ -87,7 +87,7 @@ extern EMSCRIPTEN_KEEPALIVE int godot_js_main(int argc, char *argv[]) {
 	ResourceLoader::set_abort_on_missing_resources(false);
 
 	Main::start();
-	os->get_main_loop()->init();
+	os->get_main_loop()->initialize();
 	emscripten_set_main_loop(main_loop_callback, -1, false);
 	// Immediately run the first iteration.
 	// We are inside an animation frame, we want to immediately draw on the newly setup canvas.
diff --git a/platform/javascript/os_javascript.cpp b/platform/javascript/os_javascript.cpp
index 3fb5d4ad6a..b922b2ba91 100644
--- a/platform/javascript/os_javascript.cpp
+++ b/platform/javascript/os_javascript.cpp
@@ -106,14 +106,18 @@ void OS_JavaScript::finalize() {
 
 // Miscellaneous
 
-Error OS_JavaScript::execute(const String &p_path, const List<String> &p_arguments, bool p_blocking, ProcessID *r_child_id, String *r_pipe, int *r_exitcode, bool read_stderr, Mutex *p_pipe_mutex) {
+Error OS_JavaScript::execute(const String &p_path, const List<String> &p_arguments, String *r_pipe, int *r_exitcode, bool read_stderr, Mutex *p_pipe_mutex) {
+	return create_process(p_path, p_arguments);
+}
+
+Error OS_JavaScript::create_process(const String &p_path, const List<String> &p_arguments, ProcessID *r_child_id) {
 	Array args;
 	for (const List<String>::Element *E = p_arguments.front(); E; E = E->next()) {
 		args.push_back(E->get());
 	}
 	String json_args = JSON::print(args);
 	int failed = godot_js_os_execute(json_args.utf8().get_data());
-	ERR_FAIL_COND_V_MSG(failed, ERR_UNAVAILABLE, "OS::execute() must be implemented in JavaScript via 'engine.setOnExecute' if required.");
+	ERR_FAIL_COND_V_MSG(failed, ERR_UNAVAILABLE, "OS::execute() or create_process() must be implemented in JavaScript via 'engine.setOnExecute' if required.");
 	return OK;
 }
 
diff --git a/platform/javascript/os_javascript.h b/platform/javascript/os_javascript.h
index 9c8da0c898..8db62d9d1c 100644
--- a/platform/javascript/os_javascript.h
+++ b/platform/javascript/os_javascript.h
@@ -70,7 +70,8 @@ public:
 	MainLoop *get_main_loop() const override;
 	bool main_loop_iterate();
 
-	Error execute(const String &p_path, const List<String> &p_arguments, bool p_blocking = true, ProcessID *r_child_id = nullptr, String *r_pipe = nullptr, int *r_exitcode = nullptr, bool read_stderr = false, Mutex *p_pipe_mutex = nullptr) override;
+	Error execute(const String &p_path, const List<String> &p_arguments, String *r_pipe = nullptr, int *r_exitcode = nullptr, bool read_stderr = false, Mutex *p_pipe_mutex = nullptr) override;
+	Error create_process(const String &p_path, const List<String> &p_arguments, ProcessID *r_child_id = nullptr) override;
 	Error kill(const ProcessID &p_pid) override;
 	int get_process_id() const override;