diff --git a/vlib/builtin/js/builtin.v b/vlib/builtin/js/builtin.v
index ce9093af98..5f97a29226 100644
--- a/vlib/builtin/js/builtin.v
+++ b/vlib/builtin/js/builtin.v
@@ -32,12 +32,38 @@ struct Option {
 	err   Error
 }
 
+// IError holds information about an error instance
+pub interface IError {
+	msg string
+	code int
+}
+
+// Error is the default implementation of IError, that is returned by e.g. `error()`
 pub struct Error {
 pub:
 	msg  string
 	code int
 }
 
+const none__ = IError(&None__{})
+
+struct None__ {
+	msg  string
+	code int
+}
+
+fn (_ None__) str() string {
+	return 'none'
+}
+
+pub fn (err IError) str() string {
+	return match err {
+		None__ { 'none' }
+		Error { err.msg }
+		else { '$err.type_name(): $err.msg' }
+	}
+}
+
 pub fn (o Option) str() string {
 	if o.state == 0 {
 		return 'Option{ ok }'
@@ -48,21 +74,28 @@ pub fn (o Option) str() string {
 	return 'Option{ error: "$o.err" }'
 }
 
-pub fn error(s string) Option {
-	return Option{
-		state: 2
-		err: Error{
-			msg: s
-		}
+[if trace_error ?]
+fn trace_error(x string) {
+	eprintln('> ${@FN} | $x')
+}
+
+// error returns a default error instance containing the error given in `message`.
+// Example: `if ouch { return error('an error occurred') }`
+[inline]
+pub fn error(message string) IError {
+	trace_error(message)
+	return &Error{
+		msg: message
 	}
 }
 
-pub fn error_with_code(s string, code int) Option {
-	return Option{
-		state: 2
-		err: Error{
-			msg: s
-			code: code
-		}
+// error_with_code returns a default error instance containing the given `message` and error `code`.
+// `if ouch { return error_with_code('an error occurred', 1) }`
+[inline]
+pub fn error_with_code(message string, code int) IError {
+	// trace_error('$message | code: $code')
+	return &Error{
+		msg: message
+		code: code
 	}
 }
diff --git a/vlib/builtin/js/byte.js.v b/vlib/builtin/js/byte.js.v
index a2508db399..af1803b29d 100644
--- a/vlib/builtin/js/byte.js.v
+++ b/vlib/builtin/js/byte.js.v
@@ -2,7 +2,15 @@ module builtin
 
 pub fn (b byte) is_space() bool {
 	mut result := false
-	#result = /^\s*$/.test(String.fromCharCode(b))
+	#result.val = /^\s*$/.test(String.fromCharCode(b))
+
+	return result
+}
+
+pub fn (c byte) is_letter() bool {
+	result := false
+
+	#result.val = (c.val >= `a`.charCodeAt() && c.val <= `z`.charCodeAt()) || (c.val >= `A`.charCodeAt() && c.val <= `Z`.charCodeAt())
 
 	return result
 }
diff --git a/vlib/builtin/js/string.js.v b/vlib/builtin/js/string.js.v
index f209fb8d6d..ec95bd6bb6 100644
--- a/vlib/builtin/js/string.js.v
+++ b/vlib/builtin/js/string.js.v
@@ -541,3 +541,168 @@ pub fn (s string) split_nth(delim string, nth int) []string {
 		}
 	}
 }
+
+struct RepIndex {
+	idx     int
+	val_idx int
+}
+
+// replace_each replaces all occurences of the string pairs given in `vals`.
+// Example: assert 'ABCD'.replace_each(['B','C/','C','D','D','C']) == 'AC/DC'
+[direct_array_access]
+pub fn (s string) replace_each(vals []string) string {
+	if s.len == 0 || vals.len == 0 {
+		return s.clone()
+	}
+
+	if vals.len % 2 != 0 {
+		eprintln('string.replace_each(): odd number of strings')
+		return s.clone()
+	}
+
+	// `rep` - string to replace
+	// `with_` - string to replace with_
+	// Remember positions of all rep strings, and calculate the length
+	// of the new string to do just one allocation.
+
+	mut idxs := []RepIndex{}
+	mut idx := 0
+	s_ := s.clone()
+	#function setCharAt(str,index,chr) {
+	#if(index > str.length-1) return str;
+	#return str.substring(0,index) + chr + str.substring(index+1);
+	#}
+
+	for rep_i := 0; rep_i < vals.len; rep_i += 2 {
+		rep := vals[rep_i]
+		mut with_ := vals[rep_i + 1]
+		with_ = with_
+		for {
+			idx = s_.index_after(rep, idx)
+			if idx == -1 {
+				break
+			}
+
+			for i in 0 .. rep.len {
+				mut j_ := i
+				j_ = j_
+				#s_.str = setCharAt(s_.str,idx + i, String.fromCharCode(127))
+			}
+
+			idxs << RepIndex{
+				idx: idx
+				val_idx: rep_i
+			}
+			idx += rep.len
+		}
+	}
+
+	if idxs.len == 0 {
+		return s.clone()
+	}
+
+	idxs.sort(a.idx < b.idx)
+
+	mut b := ''
+	mut idx_pos := 0
+	mut cur_idx := idxs[idx_pos]
+	mut b_i := 0
+	for i := 0; i < s.len; i++ {
+		if i == cur_idx.idx {
+			rep := vals[cur_idx.val_idx]
+			with_ := vals[cur_idx.val_idx + 1]
+			for j in 0 .. with_.len {
+				mut j_ := j
+				j_ = j_
+				#b.str = setCharAt(b.str,b_i, with_.str[j])
+				//#b.str[b_i] = with_.str[j]
+				b_i++
+			}
+			i += rep.len - 1
+			idx_pos++
+			if idx_pos < idxs.len {
+				cur_idx = idxs[idx_pos]
+			}
+		} else {
+			#b.str = setCharAt(b.str,b_i,s.str[i]) //b.str[b_i] = s.str[i]
+			b_i++
+		}
+	}
+
+	return b
+}
+
+// last_index returns the position of the last occurence of the input string.
+fn (s string) last_index_(p string) int {
+	if p.len > s.len || p.len == 0 {
+		return -1
+	}
+	mut i := s.len - p.len
+	for i >= 0 {
+		mut j := 0
+		for j < p.len && s[i + j] == p[j] {
+			j++
+		}
+		if j == p.len {
+			return i
+		}
+		i--
+	}
+	return -1
+}
+
+// last_index returns the position of the last occurence of the input string.
+pub fn (s string) last_index(p string) ?int {
+	idx := s.last_index_(p)
+	if idx == -1 {
+		return none
+	}
+	return idx
+}
+
+pub fn (s string) trim_space() string {
+	res := ''
+	#res.str = s.str.trim()
+
+	return res
+}
+
+pub fn (s string) index_after(p string, start int) int {
+	if p.len > s.len {
+		return -1
+	}
+
+	mut strt := start
+	if start < 0 {
+		strt = 0
+	}
+	if start >= s.len {
+		return -1
+	}
+	mut i := strt
+
+	for i < s.len {
+		mut j := 0
+		mut ii := i
+		for j < p.len && s[ii] == p[j] {
+			j++
+			ii++
+		}
+
+		if j == p.len {
+			return i
+		}
+		i++
+	}
+	return -1
+}
+
+pub fn (s string) split_into_lines() []string {
+	mut res := []string{}
+	#let i = 0
+	#s.str.split('\n').forEach((str) => {
+	#res.arr[i] = new string(str);
+	#})
+
+	return res
+}
diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 1b56a4e24f..7caf9e5063 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -359,6 +359,7 @@ pub fn (s string) replace_each(vals []string) string {
 		with := vals[rep_i + 1]
 		for {
 			idx = s_.index_after(rep, idx)
+
 			if idx == -1 {
 				break
 			}
@@ -374,6 +375,7 @@ pub fn (s string) replace_each(vals []string) string {
 				idx: idx
 				val_idx: rep_i
 			}
+
 			idx += rep.len
 			new_len += with.len - rep.len
 		}
diff --git a/vlib/os_js/file.js.v b/vlib/os/file.js.v
similarity index 95%
rename from vlib/os_js/file.js.v
rename to vlib/os/file.js.v
index a7541c52d3..abaeeab2b4 100644
--- a/vlib/os_js/file.js.v
+++ b/vlib/os/file.js.v
@@ -1,4 +1,4 @@
-module os_js
+module os
 
 pub struct File {
 pub:
@@ -128,3 +128,9 @@ pub fn (mut f File) write_string(s string) ?int {
 	nbytes := f.write(s.bytes()) ?
 	return nbytes
 }
+
+pub fn (mut f File) close() {
+	#f.valueOf().fd.close()
+}
+
+pub fn (mut f File) write_full_buffer(s voidptr, buffer_len size_t) ? {}
diff --git a/vlib/os/os.c.v b/vlib/os/os.c.v
new file mode 100644
index 0000000000..b8c5070704
--- /dev/null
+++ b/vlib/os/os.c.v
@@ -0,0 +1,21 @@
+module os
+
+// write_file_array writes the data in `buffer` to a file in `path`.
+pub fn write_file_array(path string, buffer array) ? {
+	mut f := create(path) ?
+	unsafe { f.write_full_buffer(buffer.data, size_t(buffer.len * buffer.element_size)) ? }
+	f.close()
+}
+
+pub fn glob(patterns ...string) ?[]string {
+	mut matches := []string{}
+	for pattern in patterns {
+		native_glob_pattern(pattern, mut matches) ?
+	}
+	matches.sort()
+	return matches
+}
+
+pub const (
+	args = []string{}
+)
diff --git a/vlib/os/os.js.v b/vlib/os/os.js.v
index a1342f466d..6ba3c77a48 100644
--- a/vlib/os/os.js.v
+++ b/vlib/os/os.js.v
@@ -4,9 +4,9 @@ module os
 #const $path = require('path');
 
 pub const (
-	args           = []string{}
 	path_delimiter = '/'
 	path_separator = '/'
+	args           = []string{}
 )
 
 $if js_node {
diff --git a/vlib/os/os.v b/vlib/os/os.v
index 47ea85b0c3..4574156324 100644
--- a/vlib/os/os.v
+++ b/vlib/os/os.v
@@ -4,7 +4,6 @@
 module os
 
 pub const (
-	args          = []string{}
 	max_path_len  = 4096
 	wd_at_startup = getwd()
 )
@@ -344,22 +343,15 @@ pub fn write_file(path string, text string) ? {
 	f.close()
 }
 
-// write_file_array writes the data in `buffer` to a file in `path`.
-pub fn write_file_array(path string, buffer array) ? {
-	mut f := create(path) ?
-	unsafe { f.write_full_buffer(buffer.data, size_t(buffer.len * buffer.element_size)) ? }
-	f.close()
-}
-
 // executable_fallback is used when there is not a more platform specific and accurate implementation.
 // It relies on path manipulation of os.args[0] and os.wd_at_startup, so it may not work properly in
 // all cases, but it should be better, than just using os.args[0] directly.
 fn executable_fallback() string {
-	if os.args.len == 0 {
+	if args.len == 0 {
 		// we are early in the bootstrap, os.args has not been initialized yet :-|
 		return ''
 	}
-	mut exepath := os.args[0]
+	mut exepath := args[0]
 	$if windows {
 		if !exepath.contains('.exe') {
 			exepath += '.exe'
@@ -639,12 +631,3 @@ pub fn execute_or_exit(cmd string) Result {
 	}
 	return res
 }
-
-pub fn glob(patterns ...string) ?[]string {
-	mut matches := []string{}
-	for pattern in patterns {
-		native_glob_pattern(pattern, mut matches) ?
-	}
-	matches.sort()
-	return matches
-}
diff --git a/vlib/os/os_js.js.v b/vlib/os/os_js.js.v
index c198ce95c4..008a7c13cb 100644
--- a/vlib/os/os_js.js.v
+++ b/vlib/os/os_js.js.v
@@ -15,22 +15,25 @@ pub fn mkdir(path string) ?bool {
 
 pub fn is_dir(path string) bool {
 	res := false
-	#res.val = $fs.existsSync(path,str) && $fs.lstatSync(path.str).isDirectory()
-
+	$if js_node {
+		#res.val = $fs.existsSync(path,str) && $fs.lstatSync(path.str).isDirectory()
+	}
 	return res
 }
 
 pub fn is_link(path string) bool {
 	res := false
-	#res.val = $fs.existsSync(path.str) && $fs.lstatSync(path.str).isSymbolicLink()
-
+	$if js_node {
+		#res.val = $fs.existsSync(path.str) && $fs.lstatSync(path.str).isSymbolicLink()
+	}
 	return res
 }
 
 pub fn exists(path string) bool {
 	res := false
-	#res.val = $fs.existsSync(path.str)
-
+	$if js_node {
+		#res.val = $fs.existsSync(path.str)
+	}
 	return res
 }
 
@@ -40,8 +43,85 @@ pub fn ls(path string) ?[]string {
 	}
 
 	result := []string{}
-	#let i = 0
-	#$fs.readdirSync(path.str).forEach((path) => result.arr[i++] = new builtin.string(path))
-
+	$if js_node {
+		#let i = 0
+		#$fs.readdirSync(path.str).forEach((path) => result.arr[i++] = new builtin.string(path))
+	}
 	return result
 }
+
+pub fn get_raw_line() string {
+	return ''
+}
+
+pub fn executable() string {
+	return ''
+}
+
+pub fn is_executable(path string) bool {
+	eprintln('TODO: There is no isExecutable on fs.stats')
+	return false
+}
+
+pub fn rmdir(path string) ? {
+	$if js_node {
+		err := ''
+		#try {
+		#$fs.rmdirSync(path.str)
+		#return;
+		#} catch (e) {
+		#err.str = 'Failed to remove "' + path.str + '": ' + e.toString()
+		#}
+
+		return error(err)
+	}
+}
+
+pub fn rm(path string) ? {
+	$if js_node {
+		err := ''
+		#try {
+		#$fs.rmSync(path.str)
+		#return;
+		#} catch (e) {
+		#err.str = 'Failed to remove "' + path.str + '": ' + e.toString()
+		#}
+
+		return error(err)
+	}
+}
+
+pub fn cp(src string, dst string) ? {
+	$if js_node {
+		err := ''
+		#try {
+		#$fs.cpSync(src.str,dst.str);
+		#return;
+		#} catch (e) {
+		#err.str = 'failed to copy ' + src.str + ' to ' + dst.str + ': ' + e.toString();
+		#}
+
+		return error(err)
+	}
+}
+
+pub fn read_file(s string) ?string {
+	mut err := ''
+	err = err
+	res := ''
+	#try {
+	#res.str = $fs.readFileSync(s.str).toString()
+	#} catch (e) {
+	#err.str = 'Failed to read file: ' + e.toString()
+	#return error(err)
+	#}
+
+	return res
+}
+
+pub fn getwd() string {
+	res := ''
+	#res.str = $process.cwd()
+
+	return res
+}
diff --git a/vlib/os_js/environment.js.v b/vlib/os_js/environment.js.v
deleted file mode 100644
index 0f69f094c5..0000000000
--- a/vlib/os_js/environment.js.v
+++ /dev/null
@@ -1,31 +0,0 @@
-module os_js
-
-// setenv sets the value of an environment variable with `name` to `value`.
-pub fn setenv(key string, val string, overwrite bool) {
-	#if ($process.env[key] && !(overwrite.valueOf())) return;
-	#$process.env[key] = val + '';
-}
-
-// `getenv` returns the value of the environment variable named by the key.
-pub fn getenv(key string) string {
-	mut res := ''
-	#if ($process.env[key]) res = new builtin.string($process.env[key])
-
-	return res
-}
-
-// unsetenv clears an environment variable with `name`.
-pub fn unsetenv(name string) int {
-	#$process.env[name] = ""
-
-	return 1
-}
-
-pub fn environ() map[string]string {
-	mut res := map[string]string{}
-	#for (const key in $process.env) {
-	#res.map.set(key,$process.env[key])
-	#}
-
-	return res
-}
diff --git a/vlib/os_js/os.js.v b/vlib/os_js/os.js.v
deleted file mode 100644
index 2fb088a865..0000000000
--- a/vlib/os_js/os.js.v
+++ /dev/null
@@ -1,95 +0,0 @@
-module os_js
-
-#const $fs = require('fs');
-#const $path = require('path');
-
-pub const (
-	args = []string{}
-)
-
-$if js_node {
-	#$process.argv.forEach(function(val,index) { args.arr[index] = new string(val); })
-}
-
-// real_path returns the full absolute path for fpath, with all relative ../../, symlinks and so on resolved.
-// See http://pubs.opengroup.org/onlinepubs/9699919799/functions/realpath.html
-// Also https://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
-// and https://insanecoding.blogspot.com/2007/11/implementing-realpath-in-c.html
-// NB: this particular rabbit hole is *deep* ...
-pub fn real_path(fpath string) string {
-	$if js_node {
-		mut res := ''
-		#res = new string( $fs.realpathSync(fpath))
-
-		return res
-	} $else {
-		return fpath
-	}
-}
-
-// flush will flush the stdout buffer.
-pub fn flush() {
-	$if js_node {
-		#$process.stdout.write('')
-	}
-}
-
-// chmod change file access attributes of `path` to `mode`.
-// Octals like `0o600` can be used.
-pub fn chmod(path string, mode int) {
-	$if js_node {
-		#$fs.chmodSync(''+path,mode.valueOf())
-	}
-}
-
-// chown changes the owner and group attributes of `path` to `owner` and `group`.
-// Octals like `0o600` can be used.
-pub fn chown(path string, owner int, group int) {
-	$if js_node {
-		#$fs.chownSync(''+path,owner.valueOf(),group.valueOf())
-	}
-}
-
-pub fn temp_dir() string {
-	mut res := ''
-	$if js_node {
-		#res = new builtin.string($os.tmpdir())
-	}
-	return res
-}
-
-pub fn home_dir() string {
-	mut res := ''
-	$if js_node {
-		#res = new builtin.string($os.homedir())
-	}
-	return res
-}
-
-// join_path returns a path as string from input string parameter(s).
-pub fn join_path(base string, dirs ...string) string {
-	mut result := []string{}
-	result << base.trim_right('\\/')
-	for d in dirs {
-		result << d
-	}
-	mut path_sep := ''
-	#path_sep = $path.sep;
-
-	res := result.join(path_sep)
-	return res
-}
-
-pub fn execute(cmd string) Result {
-	mut exit_code := 0
-	mut stdout := ''
-	#let commands = cmd.str.split(' ');
-	#let output = $child_process.spawnSync(commands[0],commands.slice(1,commands.length));
-	#exit_code = new builtin.int(output.status)
-	#stdout = new builtin.string(output.stdout + '')
-
-	return Result{
-		exit_code: exit_code
-		output: stdout
-	}
-}
diff --git a/vlib/os_js/os.v b/vlib/os_js/os.v
deleted file mode 100644
index 8b4e160ea4..0000000000
--- a/vlib/os_js/os.v
+++ /dev/null
@@ -1,13 +0,0 @@
-module os_js
-
-pub const (
-	// todo(playX): NodeJS does not seem to have any path limit?
-	max_path_len = 4096
-)
-
-pub struct Result {
-pub:
-	exit_code int
-	output    string
-	// stderr string // TODO
-}
diff --git a/vlib/os_js/process.js.v b/vlib/os_js/process.js.v
deleted file mode 100644
index e5574d8f28..0000000000
--- a/vlib/os_js/process.js.v
+++ /dev/null
@@ -1,173 +0,0 @@
-module os_js
-
-#const $child_process = require('child_process')
-
-// ProcessState.not_started - the process has not yet started
-// ProcessState.running - the process is currently running
-// ProcessState.stopped - the process was running, but was stopped temporarily
-// ProcessState.exited - the process has finished/exited
-// ProcessState.aborted - the process was terminated by a signal
-// ProcessState.closed - the process resources like opened file descriptors were freed/discarded, final state.
-pub enum ProcessState {
-	not_started
-	running
-	stopped
-	exited
-	aborted
-	closed
-}
-
-// todo(playX): fix reference member access in JS backend
-[heap]
-pub struct Process {
-pub:
-	filename string
-pub mut:
-	pid    voidptr
-	code   int = -1
-	status ProcessState = .not_started
-	// the current status of the process
-	err           string   // if the process fails, contains the reason why
-	args          []string // the arguments that the command takes
-	env_is_custom bool     // true, when the environment was customized with .set_environment
-	env           []string // the environment with which the process was started  (list of 'var=val')
-	use_stdio_ctl bool     // when true, then you can use p.stdin_write(), p.stdout_slurp() and p.stderr_slurp()
-	use_pgroup    bool     // when true, the process will create a new process group, enabling .signal_pgkill()
-	stdio_fd      [3]int   // the stdio file descriptors for the child process, used only by the nix implementation
-}
-
-// new_process - create a new process descriptor
-// NB: new does NOT start the new process.
-// That is done because you may want to customize it first,
-// by calling different set_ methods on it.
-// In order to start it, call p.run() or p.wait()
-pub fn new_process(filename string) &Process {
-	return &Process{
-		filename: filename
-		stdio_fd: [-1, -1, -1]!
-	}
-}
-
-// set_args - set the arguments for the new process
-pub fn (mut p Process) set_args(pargs []string) {
-	if p.status != .not_started {
-		return
-	}
-	p.args = pargs
-	return
-}
-
-// set_environment - set a custom environment variable mapping for the new process
-pub fn (mut p Process) set_environment(envs map[string]string) {
-	if p.status != .not_started {
-		return
-	}
-	p.env_is_custom = true
-	p.env = []string{}
-	for k, v in envs {
-		p.env << '$k=$v'
-	}
-	return
-}
-
-fn (mut p Process) spawn_internal() {
-	#p.val.pid = $child_process.spawn(
-	#p.val.filename+'',
-	#p.val.args.arr.map((x) => x.valueOf() + ''),
-	#{
-	#env: (p.val.env_is_custom ? p.val.env : $process.env),
-	#})
-	#p.val.pid.on('error', function (err) { builtin.panic('Failed to start subprocess') })
-
-	p.status = .running
-	// todo(playX): stderr,stdin
-	if p.use_stdio_ctl {
-		#p.val.pid.stdout.pipe(process.stdout)
-		#p.val.pid.stdin.pipe(process.stdin)
-		#p.val.pid.stderr.pipe(process.stderr)
-	}
-}
-
-pub fn (mut p Process) run() {
-	if p.status != .not_started {
-		return
-	}
-	p.spawn_internal()
-	return
-}
-
-pub fn (mut p Process) signal_kill() {
-	if p.status !in [.running, .stopped] {
-		return
-	}
-	#p.val.pid.kill('SIGKILL');
-
-	p.status = .aborted
-}
-
-pub fn (mut p Process) signal_stop() {
-	if p.status !in [.running, .stopped] {
-		return
-	}
-	#p.val.pid.kill('SIGSTOP');
-
-	p.status = .aborted
-}
-
-pub fn (mut p Process) signal_continue() {
-	if p.status != .stopped {
-		return
-	}
-	#p.val.pid.kill('SIGCONT');
-
-	p.status = .running
-	return
-}
-
-pub fn (mut p Process) wait() {
-	if p.status == .not_started {
-		p.spawn_internal()
-	}
-	if p.status !in [.running, .stopped] {
-		return
-	}
-
-	p.wait_internal()
-	return
-}
-
-fn (mut p Process) wait_internal() {
-	#p.val.pid.on('exit', function (code) { console.log(code) })
-}
-
-pub fn (mut p Process) set_redirect_stdio() {
-	p.use_stdio_ctl = true
-	return
-}
-
-pub fn (mut p Process) stdin_write(s string) {
-	p.check_redirection_call('stdin_write')
-	#p.val.pid.stdin.write(s)
-}
-
-// todo(playX): probably does not work
-
-// will read from stdout pipe, will only return when EOF (end of file) or data
-// means this will block unless there is data
-pub fn (mut p Process) stdout_slurp() string {
-	p.check_redirection_call('stdout_slurp')
-	mut res := ''
-	#p.val.pid.stdout.on('data', function (data) { res = new builtin.string(data) })
-
-	return res
-}
-
-// _check_redirection_call - should be called just by stdxxx methods
-fn (mut p Process) check_redirection_call(fn_name string) {
-	if !p.use_stdio_ctl {
-		panic('Call p.set_redirect_stdio() before calling p.$fn_name')
-	}
-	if p.status == .not_started {
-		panic('Call p.${fn_name}() after you have called p.run()')
-	}
-}
diff --git a/vlib/v/gen/js/builtin_types.v b/vlib/v/gen/js/builtin_types.v
index ea792ad90b..d5b915e8f2 100644
--- a/vlib/v/gen/js/builtin_types.v
+++ b/vlib/v/gen/js/builtin_types.v
@@ -338,7 +338,7 @@ fn (mut g JsGen) gen_builtin_type_defs() {
 				g.gen_builtin_prototype(
 					typ_name: typ_name
 					default_value: 'new Number(0)'
-					constructor: 'this.val = typeof(val) == "string" ? val.charCodeAt() : (val | 0)'
+					constructor: 'if (typeof(val) == "string") { this.val = val.charCodeAt() } else if (val instanceof string) { this.val = val.str.charCodeAt(); } else { this.val =  val | 0 }'
 					value_of: 'this.val | 0'
 					to_string: 'new string(this.val + "")'
 					eq: 'this.valueOf() === other.valueOf()'
diff --git a/vlib/v/gen/js/js.v b/vlib/v/gen/js/js.v
index eb2a2bc4c3..3aeb9fe099 100644
--- a/vlib/v/gen/js/js.v
+++ b/vlib/v/gen/js/js.v
@@ -525,6 +525,111 @@ fn (mut g JsGen) gen_global_decl(node ast.GlobalDecl) {
 	}
 }
 
+fn (mut g JsGen) stmt_no_semi(node ast.Stmt) {
+	g.stmt_start_pos = g.ns.out.len
+	match node {
+		ast.EmptyStmt {}
+		ast.AsmStmt {
+			panic('inline asm is not supported by js')
+		}
+		ast.AssertStmt {
+			g.write_v_source_line_info(node.pos)
+			g.gen_assert_stmt(node)
+		}
+		ast.AssignStmt {
+			g.write_v_source_line_info(node.pos)
+			g.gen_assign_stmt(node, false)
+		}
+		ast.Block {
+			g.write_v_source_line_info(node.pos)
+			g.gen_block(node)
+			g.writeln('')
+		}
+		ast.BranchStmt {
+			g.write_v_source_line_info(node.pos)
+			g.gen_branch_stmt(node)
+		}
+		ast.CompFor {}
+		ast.ConstDecl {
+			g.write_v_source_line_info(node.pos)
+			g.gen_const_decl(node)
+		}
+		ast.DeferStmt {
+			g.defer_stmts << node
+		}
+		ast.EnumDecl {
+			g.write_v_source_line_info(node.pos)
+			g.gen_enum_decl(node)
+			g.writeln('')
+		}
+		ast.ExprStmt {
+			g.write_v_source_line_info(node.pos)
+			g.gen_expr_stmt_no_semi(node)
+		}
+		ast.FnDecl {
+			g.write_v_source_line_info(node.pos)
+			g.fn_decl = unsafe { &node }
+			g.gen_fn_decl(node)
+		}
+		ast.ForCStmt {
+			g.write_v_source_line_info(node.pos)
+			g.gen_for_c_stmt(node)
+			g.writeln('')
+		}
+		ast.ForInStmt {
+			g.write_v_source_line_info(node.pos)
+			g.gen_for_in_stmt(node)
+			g.writeln('')
+		}
+		ast.ForStmt {
+			g.write_v_source_line_info(node.pos)
+			g.gen_for_stmt(node)
+			g.writeln('')
+		}
+		ast.GlobalDecl {
+			g.write_v_source_line_info(node.pos)
+			g.gen_global_decl(node)
+			g.writeln('')
+		}
+		ast.GotoLabel {
+			g.write_v_source_line_info(node.pos)
+			g.writeln('${g.js_name(node.name)}:')
+		}
+		ast.GotoStmt {
+			// skip: JS has no goto
+		}
+		ast.HashStmt {
+			g.write_v_source_line_info(node.pos)
+			g.gen_hash_stmt(node)
+		}
+		ast.Import {
+			g.ns.imports[node.mod] = node.alias
+		}
+		ast.InterfaceDecl {
+			g.write_v_source_line_info(node.pos)
+			g.gen_interface_decl(node)
+		}
+		ast.Module {
+			// skip: namespacing implemented externally
+		}
+		ast.NodeError {}
+		ast.Return {
+			if g.defer_stmts.len > 0 {
+				g.gen_defer_stmts()
+			}
+			g.gen_return_stmt(node)
+		}
+		ast.SqlStmt {}
+		ast.StructDecl {
+			g.write_v_source_line_info(node.pos)
+			g.gen_struct_decl(node)
+		}
+		ast.TypeDecl {
+			// skip JS has no typedecl
+		}
+	}
+}
+
 fn (mut g JsGen) stmt(node ast.Stmt) {
 	g.stmt_start_pos = g.ns.out.len
 	match node {
@@ -538,7 +643,7 @@ fn (mut g JsGen) stmt(node ast.Stmt) {
 		}
 		ast.AssignStmt {
 			g.write_v_source_line_info(node.pos)
-			g.gen_assign_stmt(node)
+			g.gen_assign_stmt(node, true)
 		}
 		ast.Block {
 			g.write_v_source_line_info(node.pos)
@@ -860,7 +965,7 @@ fn (mut g JsGen) gen_assert_stmt(a ast.AssertStmt) {
 	g.writeln('}')
 }
 
-fn (mut g JsGen) gen_assign_stmt(stmt ast.AssignStmt) {
+fn (mut g JsGen) gen_assign_stmt(stmt ast.AssignStmt, semicolon bool) {
 	if stmt.left.len > stmt.right.len {
 		// multi return
 		g.write('const [')
@@ -874,7 +979,9 @@ fn (mut g JsGen) gen_assign_stmt(stmt ast.AssignStmt) {
 		}
 		g.write('] = ')
 		g.expr(stmt.right[0])
-		g.writeln(';')
+		if semicolon {
+			g.writeln(';')
+		}
 	} else {
 		// `a := 1` | `a,b := 1,2`
 		for i, left in stmt.left {
@@ -996,10 +1103,12 @@ fn (mut g JsGen) gen_assign_stmt(stmt ast.AssignStmt) {
 					g.cast_stack.delete_last()
 				}
 			}
-			if g.inside_loop {
-				g.write('; ')
-			} else {
-				g.writeln(';')
+			if semicolon {
+				if g.inside_loop {
+					g.write('; ')
+				} else {
+					g.writeln(';')
+				}
 			}
 		}
 	}
@@ -1072,6 +1181,10 @@ fn (mut g JsGen) gen_expr_stmt(it ast.ExprStmt) {
 	}
 }
 
+fn (mut g JsGen) gen_expr_stmt_no_semi(it ast.ExprStmt) {
+	g.expr(it.expr)
+}
+
 fn (mut g JsGen) gen_fn_decl(it ast.FnDecl) {
 	if it.no_body || it.is_method {
 		// Struct methods are handled by class generation code.
@@ -1211,7 +1324,7 @@ fn (mut g JsGen) gen_for_c_stmt(it ast.ForCStmt) {
 	}
 	g.write('; ')
 	if it.has_inc {
-		g.stmt(it.inc)
+		g.stmt_no_semi(it.inc)
 	}
 	g.writeln(') {')
 	g.stmts(it.stmts)
@@ -1349,6 +1462,7 @@ fn (mut g JsGen) gen_interface_decl(it ast.InterfaceDecl) {
 	// TODO: interfaces are always `pub`?
 	name := g.js_name(it.name)
 	g.push_pub_var('/** @type $name */\n\t\t$name: undefined')
+	g.writeln('function ${g.js_name(it.name)} (arg) { return arg; }')
 }
 
 fn (mut g JsGen) gen_return_stmt(it ast.Return) {
@@ -1629,7 +1743,7 @@ fn (mut g JsGen) gen_method_call(it ast.CallExpr) bool {
 				if it.or_block.stmts.len > 1 {
 					g.stmts(it.or_block.stmts[..it.or_block.stmts.len - 1])
 				}
-				g.write('return ')
+				// g.write('return ')
 				g.stmt(it.or_block.stmts.last())
 			}
 			.propagate {
@@ -1707,7 +1821,8 @@ fn (mut g JsGen) gen_call_expr(it ast.CallExpr) {
 				if it.or_block.stmts.len > 1 {
 					g.stmts(it.or_block.stmts[..it.or_block.stmts.len - 1])
 				}
-				g.write('return ')
+
+				//	g.write('return ')
 				g.stmt(it.or_block.stmts.last())
 			}
 			.propagate {
@@ -1928,7 +2043,8 @@ fn (mut g JsGen) match_expr(node ast.MatchExpr) {
 	}
 
 	if node.cond is ast.Ident || node.cond is ast.SelectorExpr || node.cond is ast.IntegerLiteral
-		|| node.cond is ast.StringLiteral || node.cond is ast.FloatLiteral {
+		|| node.cond is ast.StringLiteral || node.cond is ast.FloatLiteral
+		|| node.cond is ast.CallExpr {
 		cond_var = CondExpr{node.cond}
 	} else {
 		s := g.new_tmp_var()
@@ -2577,7 +2693,15 @@ fn (mut g JsGen) gen_string_literal(it ast.StringLiteral) {
 		}
 		g.write('string(')
 	}
-	g.write("\"$text\"")
+	if it.is_raw {
+		g.writeln('(function() { let s = String(); ')
+		for x in text {
+			g.writeln('s += String.fromCharCode($x);')
+		}
+		g.writeln('return s; })()')
+	} else {
+		g.write("\"$text\"")
+	}
 	if true || should_cast {
 		g.write(')')
 	}