diff --git a/CHANGELOG.md b/CHANGELOG.md
index 91b04b3ad92..a06380a5480 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@ All PRs to the Wasmer repository must add to this file.
 Blocks of changes will separated by version increments.
 
 ## **[Unreleased]**
+- [#409](https://github.com/wasmerio/wasmer/pull/409) Improved Emscripten functions to run JavascriptCore compiled to wasm
 - [#399](https://github.com/wasmerio/wasmer/pull/399) Add example of using a plugin extended from WASI
 - [#397](https://github.com/wasmerio/wasmer/pull/397) Fix WASI fs abstraction to work on Windows
 - [#390](https://github.com/wasmerio/wasmer/pull/390) Pin released wapm version and add it as a git submodule
diff --git a/lib/emscripten/src/emscripten_target.rs b/lib/emscripten/src/emscripten_target.rs
index 5b14a109948..8e107bd3c7a 100644
--- a/lib/emscripten/src/emscripten_target.rs
+++ b/lib/emscripten/src/emscripten_target.rs
@@ -15,6 +15,15 @@ pub fn getTempRet0(ctx: &mut Ctx) -> i32 {
     get_emscripten_data(ctx).temp_ret_0
 }
 
+pub fn _atexit(_ctx: &mut Ctx, _func: i32) -> i32 {
+    debug!("emscripten::_atexit");
+    // TODO: implement atexit properly
+    // __ATEXIT__.unshift({
+    //     func: func,
+    //     arg: arg
+    // });
+    0
+}
 pub fn __Unwind_Backtrace(_ctx: &mut Ctx, _a: i32, _b: i32) -> i32 {
     debug!("emscripten::__Unwind_Backtrace");
     0
@@ -45,14 +54,42 @@ pub fn _dladdr(_ctx: &mut Ctx, _a: i32, _b: i32) -> i32 {
     debug!("emscripten::_dladdr");
     0
 }
+pub fn _pthread_attr_init(_ctx: &mut Ctx, _a: i32) -> i32 {
+    debug!("emscripten::_pthread_attr_init");
+    0
+}
+pub fn _pthread_attr_destroy(_ctx: &mut Ctx, _a: i32) -> i32 {
+    debug!("emscripten::_pthread_attr_destroy");
+    0
+}
+pub fn _pthread_attr_getstack(
+    _ctx: &mut Ctx,
+    _stackaddr: i32,
+    _stacksize: i32,
+    _other: i32,
+) -> i32 {
+    debug!("emscripten::_pthread_attr_getstack");
+    // TODO: Translate from Emscripten
+    // HEAP32[stackaddr >> 2] = STACK_BASE;
+    // HEAP32[stacksize >> 2] = TOTAL_STACK;
+    0
+}
 pub fn _pthread_cond_destroy(_ctx: &mut Ctx, _a: i32) -> i32 {
     debug!("emscripten::_pthread_cond_destroy");
     0
 }
+pub fn _pthread_cond_timedwait(_ctx: &mut Ctx, _a: i32, _b: i32, _c: i32) -> i32 {
+    debug!("emscripten::_pthread_cond_timedwait");
+    0
+}
 pub fn _pthread_getspecific(_ctx: &mut Ctx, _a: i32) -> i32 {
     debug!("emscripten::_pthread_getspecific");
     0
 }
+pub fn _pthread_getattr_np(_ctx: &mut Ctx, _thread: i32, _attr: i32) -> i32 {
+    debug!("emscripten::_pthread_getattr_np");
+    0
+}
 pub fn _pthread_setspecific(_ctx: &mut Ctx, _a: i32, _b: i32) -> i32 {
     debug!("emscripten::_pthread_setspecific");
     0
@@ -69,6 +106,10 @@ pub fn _pthread_create(_ctx: &mut Ctx, _a: i32, _b: i32, _c: i32, _d: i32) -> i3
     debug!("emscripten::_pthread_create");
     0
 }
+pub fn _pthread_detach(_ctx: &mut Ctx, _a: i32) -> i32 {
+    debug!("emscripten::_pthread_detach");
+    0
+}
 pub fn _pthread_join(_ctx: &mut Ctx, _a: i32, _b: i32) -> i32 {
     debug!("emscripten::_pthread_join");
     0
diff --git a/lib/emscripten/src/exception.rs b/lib/emscripten/src/exception.rs
index 1f2b098d8ac..f37c015e530 100644
--- a/lib/emscripten/src/exception.rs
+++ b/lib/emscripten/src/exception.rs
@@ -28,3 +28,9 @@ pub fn ___cxa_uncaught_exception(_ctx: &mut Ctx) -> i32 {
     debug!("emscripten::___cxa_uncaught_exception");
     -1
 }
+
+pub fn ___cxa_pure_virtual(_ctx: &mut Ctx) {
+    debug!("emscripten::___cxa_pure_virtual");
+    // ABORT = true
+    panic!("Pure virtual function called!");
+}
diff --git a/lib/emscripten/src/lib.rs b/lib/emscripten/src/lib.rs
index c41e4b96d11..116a0e88d37 100644
--- a/lib/emscripten/src/lib.rs
+++ b/lib/emscripten/src/lib.rs
@@ -619,6 +619,7 @@ pub fn generate_emscripten_env(globals: &mut EmscriptenGlobals) -> ImportObject
         "_llvm_eh_typeid_for" => func!(crate::process::_llvm_eh_typeid_for),
         "_raise" => func!(crate::process::_raise),
         "_sem_init" => func!(crate::process::_sem_init),
+        "_sem_destroy" => func!(crate::process::_sem_destroy),
         "_sem_post" => func!(crate::process::_sem_post),
         "_sem_wait" => func!(crate::process::_sem_wait),
         "_getgrent" => func!(crate::process::_getgrent),
@@ -658,6 +659,7 @@ pub fn generate_emscripten_env(globals: &mut EmscriptenGlobals) -> ImportObject
         "___cxa_begin_catch" => func!(crate::exception::___cxa_begin_catch),
         "___cxa_end_catch" => func!(crate::exception::___cxa_end_catch),
         "___cxa_uncaught_exception" => func!(crate::exception::___cxa_uncaught_exception),
+        "___cxa_pure_virtual" => func!(crate::exception::___cxa_pure_virtual),
 
         // Time
         "_gettimeofday" => func!(crate::time::_gettimeofday),
@@ -686,6 +688,7 @@ pub fn generate_emscripten_env(globals: &mut EmscriptenGlobals) -> ImportObject
         "_llvm_cos_f64" => func!(crate::math::_llvm_cos_f64),
         "_llvm_exp2_f32" => func!(crate::math::_llvm_exp2_f32),
         "_llvm_exp2_f64" => func!(crate::math::_llvm_exp2_f64),
+        "_llvm_trunc_f64" => func!(crate::math::_llvm_trunc_f64),
         "_emscripten_random" => func!(crate::math::_emscripten_random),
 
         // Jump
@@ -704,6 +707,7 @@ pub fn generate_emscripten_env(globals: &mut EmscriptenGlobals) -> ImportObject
         "_dlsym" => func!(crate::linking::_dlsym),
 
         // wasm32-unknown-emscripten
+        "_atexit" => func!(crate::emscripten_target::_atexit),
         "setTempRet0" => func!(crate::emscripten_target::setTempRet0),
         "getTempRet0" => func!(crate::emscripten_target::getTempRet0),
         "invoke_i" => func!(crate::emscripten_target::invoke_i),
@@ -726,10 +730,15 @@ pub fn generate_emscripten_env(globals: &mut EmscriptenGlobals) -> ImportObject
         "___resumeException" => func!(crate::emscripten_target::___resumeException),
         "_dladdr" => func!(crate::emscripten_target::_dladdr),
         "_pthread_create" => func!(crate::emscripten_target::_pthread_create),
+        "_pthread_detach" => func!(crate::emscripten_target::_pthread_detach),
         "_pthread_join" => func!(crate::emscripten_target::_pthread_join),
-        "_pthread_cond_destroy" => func!(crate::emscripten_target::_pthread_cond_destroy),
+        "_pthread_attr_init" => func!(crate::emscripten_target::_pthread_attr_init),
+        "_pthread_attr_destroy" => func!(crate::emscripten_target::_pthread_attr_destroy),
+        "_pthread_attr_getstack" => func!(crate::emscripten_target::_pthread_attr_getstack),
         "_pthread_cond_init" => func!(crate::emscripten_target::_pthread_cond_init),
+        "_pthread_cond_destroy" => func!(crate::emscripten_target::_pthread_cond_destroy),
         "_pthread_cond_signal" => func!(crate::emscripten_target::_pthread_cond_signal),
+        "_pthread_cond_timedwait" => func!(crate::emscripten_target::_pthread_cond_timedwait),
         "_pthread_cond_wait" => func!(crate::emscripten_target::_pthread_cond_wait),
         "_pthread_condattr_destroy" => func!(crate::emscripten_target::_pthread_condattr_destroy),
         "_pthread_condattr_init" => func!(crate::emscripten_target::_pthread_condattr_init),
@@ -743,6 +752,7 @@ pub fn generate_emscripten_env(globals: &mut EmscriptenGlobals) -> ImportObject
         "_pthread_rwlock_unlock" => func!(crate::emscripten_target::_pthread_rwlock_unlock),
         "_pthread_setcancelstate" => func!(crate::emscripten_target::_pthread_setcancelstate),
         "_pthread_getspecific" => func!(crate::emscripten_target::_pthread_getspecific),
+        "_pthread_getattr_np" => func!(crate::emscripten_target::_pthread_getattr_np),
         "_pthread_setspecific" => func!(crate::emscripten_target::_pthread_setspecific),
         "_pthread_once" => func!(crate::emscripten_target::_pthread_once),
         "_pthread_key_create" => func!(crate::emscripten_target::_pthread_key_create),
diff --git a/lib/emscripten/src/math.rs b/lib/emscripten/src/math.rs
index e0eb10c7dc5..3256b49c53b 100644
--- a/lib/emscripten/src/math.rs
+++ b/lib/emscripten/src/math.rs
@@ -44,6 +44,11 @@ pub fn _llvm_exp2_f64(_ctx: &mut Ctx, value: f64) -> f64 {
     2f64.powf(value)
 }
 
+pub fn _llvm_trunc_f64(_ctx: &mut Ctx, value: f64) -> f64 {
+    debug!("emscripten::_llvm_trunc_f64");
+    value.trunc()
+}
+
 pub fn _emscripten_random(_ctx: &mut Ctx) -> f64 {
     debug!("emscripten::_emscripten_random");
     -1.0
diff --git a/lib/emscripten/src/process.rs b/lib/emscripten/src/process.rs
index 319dc9eb466..dbbbcebc286 100644
--- a/lib/emscripten/src/process.rs
+++ b/lib/emscripten/src/process.rs
@@ -83,7 +83,12 @@ pub fn _raise(_ctx: &mut Ctx, _one: i32) -> i32 {
 
 pub fn _sem_init(_ctx: &mut Ctx, _one: i32, _two: i32, _three: i32) -> i32 {
     debug!("emscripten::_sem_init");
-    -1
+    0
+}
+
+pub fn _sem_destroy(_ctx: &mut Ctx, _one: i32) -> i32 {
+    debug!("emscripten::_sem_destroy");
+    0
 }
 
 pub fn _sem_post(_ctx: &mut Ctx, _one: i32) -> i32 {