diff --git a/vlib/builtin/js/builtin.v b/vlib/builtin/js/builtin.v
index 1cac2f3cef..081ad60638 100644
--- a/vlib/builtin/js/builtin.v
+++ b/vlib/builtin/js/builtin.v
@@ -4,14 +4,18 @@
 
 module builtin
 
+fn (a any) toString()
+
 pub fn println(s any) {
-	JS.console.log(s)
+	// Quickfix to properly print basic types
+	// TODO: Add proper detection code for this
+	JS.console.log(s.toString())
 }
 
 pub fn print(s any) {
 	// TODO
 	// $if js.node {
-		JS.process.stdout.write(s)
+		JS.process.stdout.write(s.toString())
 	// } $else {
 	//	panic('Cannot `print` in a browser, use `println` instead')
 	// }
diff --git a/vlib/builtin/js/jsfns.js.v b/vlib/builtin/js/jsfns.js.v
index 4c023a1bfa..b65945f8a3 100644
--- a/vlib/builtin/js/jsfns.js.v
+++ b/vlib/builtin/js/jsfns.js.v
@@ -7,6 +7,23 @@
 
 module builtin
 
+pub struct JS.Number {}
+pub struct JS.String {
+	length JS.Number
+}
+pub struct JS.Boolean {}
+pub struct JS.Array {}
+pub struct JS.Map {}
+
+// Type prototype functions
+fn (v JS.String) toString() JS.String
+fn (v JS.Number) toString() JS.String
+fn (v JS.Boolean) toString() JS.String
+fn (v JS.Array) toString() JS.String
+fn (v JS.Map) toString() JS.String
+
+fn (v JS.String) slice(a int, b int) JS.String
+
 // Top level functions
 fn JS.eval(string) any
 fn JS.parseInt(string, f64) f64
@@ -63,3 +80,7 @@ fn JS.Math.round(f64) f64
 fn JS.Math.sin(f64) f64
 fn JS.Math.sqrt(f64) f64
 fn JS.Math.tan(f64) f64
+
+// JSON
+fn JS.JSON.stringify(any) string
+fn JS.JSON.parse(string) any
\ No newline at end of file
diff --git a/vlib/builtin/js/string.v b/vlib/builtin/js/string.v
new file mode 100644
index 0000000000..51ff40a13d
--- /dev/null
+++ b/vlib/builtin/js/string.v
@@ -0,0 +1,9 @@
+module builtin
+
+pub struct string {
+	str JS.String
+}
+
+pub fn (s string) slice(a int, b int) string {
+	return string(s.str.slice(a, b))
+}
diff --git a/vlib/v/gen/js/builtin_types.v b/vlib/v/gen/js/builtin_types.v
new file mode 100644
index 0000000000..f7e0417ea8
--- /dev/null
+++ b/vlib/v/gen/js/builtin_types.v
@@ -0,0 +1,260 @@
+module js
+import v.table
+
+fn (mut g JsGen) to_js_typ_def_val(s string) string {
+	mut dval := ''
+	match s {
+		'JS.Number' { dval = '0' }
+		'JS.String' { dval = '""' }
+		'JS.Boolean' { dval = 'false' }
+		'JS.Array', 'JS.Map' { dval = '' }
+		else { dval = '{}' }
+	}
+	return dval
+}
+
+fn (mut g JsGen) to_js_typ_val(t table.Type) string {
+	sym := g.table.get_type_symbol(t)
+	mut styp := ''
+	mut prefix := if g.file.mod.name == 'builtin' { 'new ' } else { '' } 
+	match sym.kind {
+		.i8, .i16, .int, .i64, .byte, .u16, .u32, .u64, .f32, .f64, .any_int, .any_float, .size_t {
+			styp = '${prefix}${g.sym_to_js_typ(sym)}(0)'
+		}
+		.bool {
+			styp = '${prefix}${g.sym_to_js_typ(sym)}(false)'
+		}
+		.string {
+			styp = '${prefix}${g.sym_to_js_typ(sym)}("")'
+		}
+		.map {
+			styp = 'new Map()'
+		}
+		.array {
+			styp = '${prefix}${g.sym_to_js_typ(sym)}()'
+		}
+		.struct_ {
+			styp = 'new ${g.js_name(sym.name)}(${g.to_js_typ_def_val(sym.name)})'
+		}
+		else {
+			// TODO
+			styp = 'undefined'
+		}
+	}
+	return styp
+}
+
+fn (mut g JsGen) sym_to_js_typ(sym table.TypeSymbol) string {
+	mut styp := ''
+	match sym.kind {
+		.i8 { styp = 'i8' }
+		.i16 { styp = 'i16' }
+		.int { styp = 'int' }
+		.i64 { styp = 'i64' }
+		.byte { styp = 'byte' }
+		.u16 { styp = 'u16' }
+		.u32 { styp = 'u32' }
+		.u64 { styp = 'u64' }
+		.f32 { styp = 'f32' }
+		.f64 { styp = 'f64' }
+		.any_int { styp = 'any_int' }
+		.any_float { styp = 'any_float' }
+		.size_t { styp = 'size_t' }
+		.bool { styp = 'bool' }
+		.string { styp = 'string' }
+		.map { styp = 'map' }
+		.array { styp = 'array' }
+		else {
+			// TODO
+			styp = 'undefined'
+		}
+	}
+	return styp
+}
+
+// V type to JS type
+pub fn (mut g JsGen) typ(t table.Type) string {
+	sym := g.table.get_type_symbol(t)
+	mut styp := ''
+	match sym.kind {
+		.placeholder {
+			// This should never happen: means checker bug
+			styp = 'any'
+		}
+		.void {
+			styp = 'void'
+		}
+		.voidptr {
+			styp = 'any'
+		}
+		.byteptr, .charptr {
+			styp = '${g.sym_to_js_typ(sym)}'
+		}
+		.i8, .i16, .int, .i64, .byte, .u16, .u32, .u64, .f32, .f64, .any_int, .any_float, .size_t {
+			styp = '${g.sym_to_js_typ(sym)}'
+		}
+		.bool {
+			styp = '${g.sym_to_js_typ(sym)}'
+		}
+		.none_ {
+			styp = 'undefined'
+		}
+		.string, .ustring, .char {
+			styp = '${g.sym_to_js_typ(sym)}'
+		}
+		// 'array_array_int' => 'number[][]'
+		.array {
+			info := sym.info as table.Array
+			styp = '${g.sym_to_js_typ(sym)}(${g.typ(info.elem_type)})'
+		}
+		.array_fixed {
+			info := sym.info as table.ArrayFixed
+			styp = '${g.sym_to_js_typ(sym)}(${g.typ(info.elem_type)})'
+		}
+		.chan {
+			styp = 'chan'
+		}
+		// 'map[string]int' => 'Map<string, number>'
+		.map {
+			info := sym.info as table.Map
+			key := g.typ(info.key_type)
+			val := g.typ(info.value_type)
+			styp = 'Map<$key, $val>'
+		}
+		.any {
+			styp = 'any'
+		}
+		// ns.Foo => alias["Foo"]["prototype"]
+		.struct_ {
+			styp = g.struct_typ(sym.name)
+		}
+		.generic_struct_inst {}
+		// 'multi_return_int_int' => '[number, number]'
+		.multi_return {
+			info := sym.info as table.MultiReturn
+			types := info.types.map(g.typ(it))
+			joined := types.join(', ')
+			styp = '[$joined]'
+		}
+		.sum_type {
+			// TODO: Implement sumtypes
+			styp = 'union_sym_type'
+		}
+		.alias {
+			// TODO: Implement aliases
+			styp = 'alias'
+		}
+		.enum_ {
+			// NB: We could declare them as TypeScript enums but TS doesn't like
+			// our namespacing so these break if declared in a different module.
+			// Until this is fixed, We need to use the type of an enum's members
+			// rather than the enum itself, and this can only be 'number' for now
+			styp = 'number'
+		}
+		// 'anon_fn_7_7_1' => '(a number, b number) => void'
+		.function {
+			info := sym.info as table.FnType
+			styp = g.fn_typ(info.func.params, info.func.return_type)
+		}
+		.interface_ {
+			styp = g.js_name(sym.name)
+		}
+		.rune {
+			styp = 'any'
+		}
+		.aggregate {
+			panic('TODO: unhandled aggregate in JS')
+		}
+	}
+	/*
+	else {
+			println('jsgen.typ: Unhandled type $t')
+			styp = sym.name
+		}
+	*/
+	if styp.starts_with('JS.') {
+		return styp[3..]
+	}
+	return styp
+}
+
+fn (mut g JsGen) fn_typ(args []table.Param, return_type table.Type) string {
+	mut res := '('
+	for i, arg in args {
+		res += '$arg.name: ${g.typ(arg.typ)}'
+		if i < args.len - 1 {
+			res += ', '
+		}
+	}
+	return res + ') => ' + g.typ(return_type)
+}
+
+fn (mut g JsGen) struct_typ(s string) string {
+	ns := get_ns(s)
+	if ns == 'JS' { return s[3..] }
+	mut name := if ns == g.ns.name { s.split('.').last() } else { g.get_alias(s) }
+	mut styp := ''
+	for i, v in name.split('.') {
+		if i == 0 {
+			styp = v
+		} else {
+			styp += '["$v"]'
+		}
+	}
+	if ns in ['', g.ns.name] {
+		return styp
+	}
+	return styp + '["prototype"]'
+}
+
+// ugly arguments but not sure a config struct would be worth it
+fn (mut g JsGen) gen_builtin_prototype(typ_name string, val_name string, default_value string, constructor string, value_of string, to_string string, extras string) {
+	g.writeln('function ${typ_name}($val_name = ${default_value}) { $constructor }')
+	g.writeln('${typ_name}.prototype = {')
+	g.inc_indent()
+	g.writeln('val: $default_value,')
+	if extras.len > 0 {
+		g.writeln('$extras,')
+	}
+	for method in g.method_fn_decls[typ_name] {
+		g.inside_def_typ_decl = true
+		g.gen_method_decl(method)
+		g.inside_def_typ_decl = false
+		g.writeln(',')
+	}
+	g.writeln('valueOf() { return $value_of },')
+	g.writeln('toString() { return $to_string }')
+	g.dec_indent()
+	g.writeln('};\n')
+}
+
+// generate builtin type definitions, used for casting and methods.
+fn (mut g JsGen) gen_builtin_type_defs() {
+	g.inc_indent()
+	for typ_name in v_types {
+		// TODO: JsDoc
+		match typ_name {
+			'i8', 'i16', 'int', 'i64', 'byte', 'u16', 'u32', 'u64', 'any_int', 'size_t' {
+				// TODO: Bounds checking
+				g.gen_builtin_prototype(typ_name, 'val', 'new Number(0)', 'this.val = val | 0;', 'this.val | 0', '(this.val | 0).toString()', '')
+			}
+			'f32', 'f64', 'any_float' {
+				g.gen_builtin_prototype(typ_name, 'val', 'new Number(0)', 'this.val = val;', 'this.val', 'this.val.toString()', '')
+			}
+			'bool' {
+				g.gen_builtin_prototype(typ_name, 'val', 'new Boolean(false)', 'this.val = val;', 'this.val', 'this.val.toString()', '')
+			}
+			'string' {
+				g.gen_builtin_prototype(typ_name, 'str', 'new String("")', 'this.str = str;', 'this.str', 'this.str.toString()', 'get length() { return this.str.length }')
+			}
+			'map' {
+				g.gen_builtin_prototype(typ_name, 'val', 'new Map()', 'this.val = val;', 'this.val', 'this.val.toString()', '')
+			}
+			'array' {
+				g.gen_builtin_prototype(typ_name, 'val', 'new Array()', 'this.val = val;', 'this.val', 'this.val.toString()', '')
+			}
+			else {}
+		}
+	}
+	g.dec_indent()
+}
\ No newline at end of file
diff --git a/vlib/v/gen/js/js.v b/vlib/v/gen/js/js.v
index a263a03652..d15a4cbae1 100644
--- a/vlib/v/gen/js/js.v
+++ b/vlib/v/gen/js/js.v
@@ -3,6 +3,7 @@ module js
 import strings
 import v.ast
 import v.table
+import v.token
 import v.pref
 import v.util
 import v.depgraph
@@ -13,7 +14,9 @@ const (
 		'default', 'delete', 'do', 'else', 'enum', 'export', 'extends', 'finally', 'for', 'function', 'if',
 		'implements', 'import', 'in', 'instanceof', 'interface', 'let', 'new', 'package', 'private', 'protected',
 		'public', 'return', 'static', 'super', 'switch', 'this', 'throw', 'try', 'typeof', 'var', 'void',
-		'while', 'with', 'yield']
+		'while', 'with', 'yield', 'Number', 'String', 'Boolean', 'Array', 'Map']
+	// used to generate type structs
+	v_types = ['i8', 'i16', 'int', 'i64', 'byte', 'u16', 'u32', 'u64', 'f32', 'f64', 'any_int', 'any_float', 'size_t', 'bool', 'string', 'map', 'array']
 	tabs        = ['', '\t', '\t\t', '\t\t\t', '\t\t\t\t', '\t\t\t\t\t', '\t\t\t\t\t\t', '\t\t\t\t\t\t\t',
 		'\t\t\t\t\t\t\t\t', '\t\t\t\t\t\t\t\t\t', '\t\t\t\t\t\t\t\t\t', '\t\t\t\t\t\t\t\t\t']
 )
@@ -32,25 +35,27 @@ struct JsGen {
 	table             &table.Table
 	pref              &pref.Preferences
 mut:
-	definitions       strings.Builder
-	ns                &Namespace
-	namespaces        map[string]&Namespace
-	doc               &JsDoc
-	enable_doc        bool
-	file              ast.File
-	tmp_count         int
-	inside_ternary    bool
-	inside_loop       bool
-	inside_map_set    bool // map.set(key, value)
-	inside_builtin    bool
-	is_test           bool
-	stmt_start_pos    int
-	defer_stmts       []ast.DeferStmt
-	fn_decl           &ast.FnDecl // pointer to the FnDecl we are currently inside otherwise 0
-	str_types         []string // types that need automatic str() generation
-	method_fn_decls   map[string][]ast.FnDecl
-	builtin_fns       []string // Functions defined in `builtin`
-	empty_line        bool
+	definitions       	strings.Builder
+	ns                	&Namespace
+	namespaces        	map[string]&Namespace
+	doc               	&JsDoc
+	enable_doc        	bool
+	file              	ast.File
+	tmp_count         	int
+	inside_ternary    	bool
+	inside_loop       	bool
+	inside_map_set    	bool // map.set(key, value)
+	inside_builtin    	bool
+	generated_builtin 	bool
+	inside_def_typ_decl bool
+	is_test           	bool
+	stmt_start_pos    	int
+	defer_stmts       	[]ast.DeferStmt
+	fn_decl           	&ast.FnDecl // pointer to the FnDecl we are currently inside otherwise 0
+	str_types         	[]string // types that need automatic str() generation
+	method_fn_decls   	map[string][]ast.FnDecl
+	builtin_fns       	[]string // Functions defined in `builtin`
+	empty_line        	bool
 }
 
 pub fn gen(files []ast.File, table &table.Table, pref &pref.Preferences) string {
@@ -89,6 +94,11 @@ pub fn gen(files []ast.File, table &table.Table, pref &pref.Preferences) string
 			imports << imp.mod
 		}
 		graph.add(g.file.mod.name, imports)
+		// builtin types
+		if g.file.mod.name == 'builtin' && !g.generated_builtin {
+			g.gen_builtin_type_defs()
+			g.generated_builtin = true
+		}
 		g.stmts(file.stmts)
 		// store the current namespace
 		g.escape_namespace()
@@ -119,6 +129,12 @@ pub fn gen(files []ast.File, table &table.Table, pref &pref.Preferences) string
 			out += '\n\t/* module exports */'
 		}
 		out += '\n\treturn {'
+		// export builtin types
+		if name == 'builtin' {
+			for typ in v_types {
+				out += '\n\t\t$typ,'
+			}
+		}
 		for i, pub_var in g.namespaces[node.name].pub_vars {
 			out += '\n\t\t$pub_var'
 			if i < g.namespaces[node.name].pub_vars.len - 1 {
@@ -136,13 +152,29 @@ pub fn gen(files []ast.File, table &table.Table, pref &pref.Preferences) string
 			}
 			out += key.replace('.', '_')
 		}
-		out += ');\n\n'
+		out += ');\n'
+		// generate builtin basic type casts
+		if name == 'builtin' {
+			out += '// builtin type casts\n'
+			out += 'const ['
+			for i, typ in v_types {
+				if i > 0 { out += ', ' }
+				out += '$typ'
+			}
+			out += '] = ['
+			for i, typ in v_types {
+				if i > 0 { out += ',' }
+				out += '\n\tfunction(val) { return new builtin.${typ}(val) }'
+			}
+			out += '\n]\n'
+		}
 	}
 	if pref.is_shared {
 		// Export, through CommonJS, the module of the entry file if `-shared` was passed
 		export := nodes[nodes.len - 1].name
-		out += 'if (typeof module === "object" && module.exports) module.exports = $export;'
+		out += 'if (typeof module === "object" && module.exports) module.exports = $export;\n'
 	}
+	out += '\n'
 	return out
 }
 
@@ -175,7 +207,7 @@ pub fn (mut g JsGen) find_class_methods(stmts []ast.Stmt) {
 			ast.FnDecl {
 				if stmt.is_method {
 					// Found struct method, store it to be generated along with the class.
-					class_name := g.table.get_type_name(stmt.receiver.typ)
+					mut class_name := g.table.get_type_name(stmt.receiver.typ)
 					// Workaround until `map[key] << val` works.
 					mut arr := g.method_fn_decls[class_name]
 					arr << stmt
@@ -199,171 +231,6 @@ pub fn (g JsGen) hashes() string {
 	return res
 }
 
-// V type to JS type
-pub fn (mut g JsGen) typ(t table.Type) string {
-	sym := g.table.get_type_symbol(t)
-	mut styp := ''
-	match sym.kind {
-		.placeholder {
-			// This should never happen: means checker bug
-			styp = 'any'
-		}
-		.void {
-			styp = 'void'
-		}
-		.voidptr {
-			styp = 'any'
-		}
-		.byteptr, .charptr {
-			styp = 'string'
-		}
-		.i8, .i16, .int, .i64, .byte, .u16, .u32, .u64, .f32, .f64, .any_int, .any_float, .size_t {
-			// TODO: Should u64 and i64 use BigInt rather than number?
-			styp = 'number'
-		}
-		.bool {
-			styp = 'boolean'
-		}
-		.none_ {
-			styp = 'undefined'
-		}
-		.string, .ustring, .char {
-			styp = 'string'
-		}
-		// 'array_array_int' => 'number[][]'
-		.array {
-			info := sym.info as table.Array
-			styp = g.typ(info.elem_type) + '[]'
-		}
-		.array_fixed {
-			info := sym.info as table.ArrayFixed
-			styp = g.typ(info.elem_type) + '[]'
-		}
-		.chan {
-			styp = 'chan'
-		}
-		// 'map[string]int' => 'Map<string, number>'
-		.map {
-			info := sym.info as table.Map
-			key := g.typ(info.key_type)
-			val := g.typ(info.value_type)
-			styp = 'Map<$key, $val>'
-		}
-		.any {
-			styp = 'any'
-		}
-		// ns.Foo => alias["Foo"]["prototype"]
-		.struct_ {
-			styp = g.struct_typ(sym.name)
-		}
-		.generic_struct_inst {}
-		// 'multi_return_int_int' => '[number, number]'
-		.multi_return {
-			info := sym.info as table.MultiReturn
-			types := info.types.map(g.typ(it))
-			joined := types.join(', ')
-			styp = '[$joined]'
-		}
-		.sum_type {
-			// TODO: Implement sumtypes
-			styp = 'union_sym_type'
-		}
-		.alias {
-			// TODO: Implement aliases
-			styp = 'alias'
-		}
-		.enum_ {
-			// NB: We could declare them as TypeScript enums but TS doesn't like
-			// our namespacing so these break if declared in a different module.
-			// Until this is fixed, We need to use the type of an enum's members
-			// rather than the enum itself, and this can only be 'number' for now
-			styp = 'number'
-		}
-		// 'anon_fn_7_7_1' => '(a number, b number) => void'
-		.function {
-			info := sym.info as table.FnType
-			styp = g.fn_typ(info.func.params, info.func.return_type)
-		}
-		.interface_ {
-			styp = g.js_name(sym.name)
-		}
-		.rune {
-			styp = 'any'
-		}
-		.aggregate {
-			panic('TODO: unhandled aggregate in JS')
-		}
-	}
-	/*
-	else {
-			println('jsgen.typ: Unhandled type $t')
-			styp = sym.name
-		}
-	*/
-	if styp.starts_with('JS.') {
-		return styp[3..]
-	}
-	return styp
-}
-
-fn (mut g JsGen) fn_typ(args []table.Param, return_type table.Type) string {
-	mut res := '('
-	for i, arg in args {
-		res += '$arg.name: ${g.typ(arg.typ)}'
-		if i < args.len - 1 {
-			res += ', '
-		}
-	}
-	return res + ') => ' + g.typ(return_type)
-}
-
-fn (mut g JsGen) struct_typ(s string) string {
-	ns := get_ns(s)
-	mut name := if ns == g.ns.name { s.split('.').last() } else { g.get_alias(s) }
-	mut styp := ''
-	for i, v in name.split('.') {
-		if i == 0 {
-			styp = v
-		} else {
-			styp += '["$v"]'
-		}
-	}
-	if ns in ['', g.ns.name] {
-		return styp
-	}
-	return styp + '["prototype"]'
-}
-
-fn (mut g JsGen) to_js_typ_val(t table.Type) string {
-	sym := g.table.get_type_symbol(t)
-	mut styp := ''
-	match sym.kind {
-		.i8, .i16, .int, .i64, .byte, .u16, .u32, .u64, .f32, .f64, .any_int, .any_float, .size_t {
-			styp = '0'
-		}
-		.bool {
-			styp = 'false'
-		}
-		.string {
-			styp = '""'
-		}
-		.map {
-			styp = 'new Map()'
-		}
-		.array {
-			styp = '[]'
-		}
-		.struct_ {
-			styp = 'new ${g.js_name(sym.name)}({})'
-		}
-		else {
-			// TODO
-			styp = 'undefined'
-		}
-	}
-	return styp
-}
-
 [inline]
 fn verror(msg string) {
 	eprintln('jsgen error: $msg')
@@ -576,9 +443,7 @@ fn (mut g JsGen) expr(node ast.Expr) {
 			// TODO
 		}
 		ast.CastExpr {
-			// JS has no types, so no need to cast
-			// Just write the expression inside
-			g.expr(node.expr)
+			g.gen_type_cast_expr(node)
 		}
 		ast.CharLiteral {
 			g.write("'$node.val'")
@@ -593,7 +458,7 @@ fn (mut g JsGen) expr(node ast.Expr) {
 			g.write('${styp}.$node.val')
 		}
 		ast.FloatLiteral {
-			g.write(node.val)
+			g.write('${g.typ(table.Type(table.f32_type))}($node.val)')
 		}
 		ast.Ident {
 			g.gen_ident(node)
@@ -611,7 +476,7 @@ fn (mut g JsGen) expr(node ast.Expr) {
 			g.gen_infix_expr(node)
 		}
 		ast.IntegerLiteral {
-			g.write(node.val)
+			g.write('${g.typ(table.Type(table.int_type))}($node.val)')
 		}
 		ast.LockExpr {
 			g.gen_lock_expr(node)
@@ -664,8 +529,9 @@ fn (mut g JsGen) expr(node ast.Expr) {
 			g.gen_string_inter_literal(node)
 		}
 		ast.StringLiteral {
-			text := node.val.replace('`', '\\`')
-			g.write('`$text`')
+			text := node.val.replace('\'', "\\'")
+			if g.file.mod.name == 'builtin' { g.write('new ') }
+			g.write("string('$text')")
 		}
 		ast.StructInit {
 			// `user := User{name: 'Bob'}`
@@ -904,6 +770,12 @@ fn (mut g JsGen) gen_method_decl(it ast.FnDecl) {
 		}
 		if !it.is_method {
 			g.write('function ')
+		} else {
+			if it.attrs.contains('js_getter') {
+				g.write('get ')
+			} else if it.attrs.contains('js_setter') {
+				g.write('set ')
+			}
 		}
 		g.write('${name}(')
 		if it.is_pub && !it.is_method {
@@ -1093,12 +965,17 @@ fn (mut g JsGen) gen_hash_stmt(it ast.HashStmt) {
 }
 
 fn (mut g JsGen) gen_struct_decl(node ast.StructDecl) {
-	if node.name.starts_with('JS.') {
+	mut name := node.name
+	if name.starts_with('JS.') {
 		return
 	}
+	if name in v_types && g.ns.name == 'builtin' {
+		return
+	}
+	js_name := g.js_name(name)
 	g.gen_attrs(node.attrs)
 	g.doc.gen_fac_fn(node.fields)
-	g.write('function ${g.js_name(node.name)}({ ')
+	g.write('function ${js_name}({ ')
 	for i, field in node.fields {
 		g.write('$field.name = ')
 		if field.has_default_expr {
@@ -1117,31 +994,41 @@ fn (mut g JsGen) gen_struct_decl(node ast.StructDecl) {
 	}
 	g.dec_indent()
 	g.writeln('};')
-	g.writeln('${g.js_name(node.name)}.prototype = {')
+	g.writeln('${js_name}.prototype = {')
 	g.inc_indent()
-	fns := g.method_fn_decls[node.name]
-	for i, field in node.fields {
+	fns := g.method_fn_decls[name]
+	for field in node.fields {
 		typ := g.typ(field.typ)
 		g.doc.gen_typ(typ)
 		g.write('$field.name: ${g.to_js_typ_val(field.typ)}')
-		if i < node.fields.len - 1 || fns.len > 0 {
-			g.writeln(',')
-		} else {
-			g.writeln('')
-		}
+		g.writeln(',')
 	}
-	for i, cfn in fns {
+	for cfn in fns {
 		g.gen_method_decl(cfn)
-		if i < fns.len - 1 {
-			g.writeln(',')
-		} else {
-			g.writeln('')
-		}
+		g.writeln(',')
 	}
+	// gen toString method
+	fn_names := fns.map(it.name)
+	if !('toString' in fn_names) {
+		g.writeln('toString() {')
+		g.inc_indent()
+		g.write('return `${js_name} {')
+		for i, field in node.fields {
+			g.write(if i == 0 { ' ' } else { ', ' })
+			match g.typ(field.typ).split('.').last() {
+				"string" { g.write('$field.name: "\${this["${field.name}"].toString()}"') }
+				else { g.write('$field.name: \${this["${field.name}"].toString()} ') }
+			}
+		}
+		g.writeln('}`')
+		g.dec_indent()
+		g.writeln('}')
+	}
+
 	g.dec_indent()
 	g.writeln('};\n')
 	if node.is_pub {
-		g.push_pub_var(node.name)
+		g.push_pub_var(name)
 	}
 }
 
@@ -1296,6 +1183,7 @@ fn (mut g JsGen) gen_ident(node ast.Ident) {
 	// TODO `is`
 	// TODO handle optionals
 	g.write(name)
+	// TODO: Generate .val for basic types
 }
 
 fn (mut g JsGen) gen_lock_expr(node ast.LockExpr) {
@@ -1392,6 +1280,7 @@ fn (mut g JsGen) gen_index_expr(expr ast.IndexExpr) {
 			g.write('.get(')
 		}
 		g.expr(expr.index)
+		g.write('.toString()')
 		if !expr.is_setter {
 			g.write(')')
 		}
@@ -1401,7 +1290,7 @@ fn (mut g JsGen) gen_index_expr(expr ast.IndexExpr) {
 			// 'string'[3] = `o`
 		} else {
 			g.expr(expr.left)
-			g.write('.charCodeAt(')
+			g.write('.str.charCodeAt(')
 			g.expr(expr.index)
 			g.write(')')
 		}
@@ -1433,10 +1322,15 @@ fn (mut g JsGen) gen_infix_expr(it ast.InfixExpr) {
 		g.expr(it.right)
 		g.write(if r_sym.kind == .map {
 			'.has('
+		} else if r_sym.kind == .string {
+			'.str.includes('
 		} else {
 			'.includes('
 		})
 		g.expr(it.left)
+		if l_sym.kind == .string {
+			g.write('.str')
+		}
 		g.write(')')
 		if it.op == .not_in {
 			g.write(')')
@@ -1454,8 +1348,12 @@ fn (mut g JsGen) gen_infix_expr(it ast.InfixExpr) {
 	} else {
 		both_are_int := int(it.left_type) in table.integer_type_idxs &&
 			int(it.right_type) in table.integer_type_idxs
+		is_arithmetic := it.op in [token.Kind.plus, .minus, .mul, .div, .mod]
+		if is_arithmetic {
+			g.write('${g.typ(g.greater_typ(it.left_type, it.right_type))}(')
+		}
 		if it.op == .div && both_are_int {
-			g.write('parseInt(')
+			g.write('((')
 		}
 		g.expr(it.left)
 		// in js == is non-strict & === is strict, always do strict
@@ -1467,13 +1365,47 @@ fn (mut g JsGen) gen_infix_expr(it ast.InfixExpr) {
 			g.write(' $it.op ')
 		}
 		g.expr(it.right)
-		// Int division: 2.5 -> 2 by prepending |0
+		// Int division: 2.5 -> 2 by appending |0
 		if it.op == .div && both_are_int {
-			g.write(',10)')
+			g.write(')|0)')
+		}
+		if is_arithmetic {
+			g.write(')')
 		}
 	}
 }
 
+fn (mut g JsGen) greater_typ(left table.Type, right table.Type) table.Type {
+	l := int(left)
+	r := int(right)
+	lr := [l,r]
+
+	if table.string_type_idx in lr { return table.Type(table.string_type_idx) }
+
+	should_float := (l in table.integer_type_idxs && r in table.float_type_idxs) || (r in table.integer_type_idxs && l in table.float_type_idxs)
+	if should_float {
+		if table.f64_type_idx in lr { return table.Type(table.f64_type_idx) }
+		if table.f32_type_idx in lr { return table.Type(table.f32_type_idx) }
+		return table.Type(table.any_flt_type)
+	}
+
+	should_int := (l in table.integer_type_idxs && r in table.integer_type_idxs)
+	if should_int {
+		// cant add to u64 - if (table.u64_type_idx in lr) { return table.Type(table.u64_type_idx) }
+		// just guessing this order
+		if table.i64_type_idx in lr { return table.Type(table.i64_type_idx) }
+		if table.u32_type_idx in lr { return table.Type(table.u32_type_idx) }
+		if table.int_type_idx in lr { return table.Type(table.int_type_idx) }
+		if table.u16_type_idx in lr { return table.Type(table.u16_type_idx) }
+		if table.i16_type_idx in lr { return table.Type(table.i16_type_idx) }
+		if table.byte_type_idx in lr { return table.Type(table.byte_type_idx) }
+		if table.i8_type_idx in lr { return table.Type(table.i8_type_idx) }
+		return table.Type(table.any_int_type_idx)
+	}
+
+	return table.Type(l)
+}
+
 fn (mut g JsGen) gen_map_init_expr(it ast.MapInit) {
 	// key_typ_sym := g.table.get_type_symbol(it.key_type)
 	// value_typ_sym := g.table.get_type_symbol(it.value_type)
@@ -1507,7 +1439,8 @@ fn (mut g JsGen) gen_selector_expr(it ast.SelectorExpr) {
 }
 
 fn (mut g JsGen) gen_string_inter_literal(it ast.StringInterLiteral) {
-	g.write('`')
+	if g.file.mod.name == 'builtin' { g.write('new ') }
+	g.write('string(`')
 	for i, val in it.vals {
 		escaped_val := val.replace('`', '\\`')
 		g.write(escaped_val)
@@ -1531,7 +1464,7 @@ fn (mut g JsGen) gen_string_inter_literal(it ast.StringInterLiteral) {
 		}
 		g.write('}')
 	}
-	g.write('`')
+	g.write('`)')
 }
 
 fn (mut g JsGen) gen_struct_init(it ast.StructInit) {
@@ -1582,3 +1515,24 @@ fn (mut g JsGen) gen_typeof_expr(it ast.TypeOf) {
 		g.write('"$sym.name"')
 	}
 }
+
+fn (mut g JsGen) gen_type_cast_expr(it ast.CastExpr) {
+	is_literal := (
+		(it.expr is ast.IntegerLiteral && it.typ in table.integer_type_idxs) ||
+		(it.expr is ast.FloatLiteral && it.typ in table.float_type_idxs)
+	)
+	typ := g.typ(it.typ)
+	if !is_literal {
+		if !(typ in v_types) || g.ns.name == 'builtin' {
+			g.write('new ')
+		}
+		g.write('${typ}(')
+	}
+	g.expr(it.expr)
+	if typ == 'string' && !(it.expr is ast.StringLiteral) {
+		g.write('.toString()')
+	}
+	if !is_literal {
+		g.write(')')
+	}
+}
\ No newline at end of file
diff --git a/vlib/v/gen/js/tests/array.v b/vlib/v/gen/js/tests/array.v
index 0c08a31719..66fa87dbe7 100644
--- a/vlib/v/gen/js/tests/array.v
+++ b/vlib/v/gen/js/tests/array.v
@@ -78,6 +78,8 @@ for i, _ in arr2 { println(i) }
 println('\n\n4 to 5\t=> ')
 for _, v in slice3 { println(v) }
 
+println(int(1.5))
+
 println('\n\n')
 
 // map
diff --git a/vlib/v/gen/js/tests/js.v b/vlib/v/gen/js/tests/js.v
index e927ecd441..0722e9f5d2 100644
--- a/vlib/v/gen/js/tests/js.v
+++ b/vlib/v/gen/js/tests/js.v
@@ -34,13 +34,16 @@ fn main() {
 	mut a := 1
 	a *= 2
 	a += 3
-	println(a) // TODO: Handle string interpolation
+	println(a)
 	mut b := hl.Aaa{}
 	b.update('an update')
 	println(b)
 	mut c := Foo{hl.Aaa{}}
 	c.a.update('another update')
 	println(c)
+	println('int(1.5) == "${int(1.5)}"')
+	d := int(10) + f32(127)
+	println('typeof (int + f32) == "${typeof(d)}"')
 	_ = 'done'
 	{
 		_ = 'block'
@@ -52,7 +55,7 @@ fn main() {
 	await := '$super: $debugger'
 	mut finally := 'implemented'
 	println('$await $finally')
-	dun := i_am_a_const * 20
+	dun := i_am_a_const * 20 + 2
 	dunn := hl.hello // External constant
 	_ = hl1.nested()
 	for i := 0; i < 10; i++ {
diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index 85e9fa79bf..d7514759d6 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -213,7 +213,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	if p.tok.kind == .name {
 		// TODO high order fn
 		name = if language == .js { p.check_js_name() } else { p.check_name() }
-		if language == .v && !p.pref.translated && util.contains_capital(name) {
+		if language == .v && !p.pref.translated && util.contains_capital(name) && p.mod != 'builtin' {
 			p.error('function names cannot contain uppercase letters, use snake_case instead')
 			return ast.FnDecl{}
 		}