js: add more tests to builtin/js and implement more builtin functions (#12049)

vlib/builtin/js/int.js.v

@@ -1,5 +1,26 @@
 module builtin
 
+pub fn (i i8) str() string {
+	mut res := ''
+	#res.str = i.val.toString()
+
+	return res
+}
+
+pub fn (i i16) str() string {
+	mut res := ''
+	#res.str = i.val.toString()
+
+	return res
+}
+
+pub fn (i u16) str() string {
+	mut res := ''
+	#res.str = i.val.toString()
+
+	return res
+}
+
 pub fn (i int) str() string {
 	mut res := ''
 	#res = new string( i )
@@ -48,3 +69,82 @@ pub fn (i int_literal) str() string {
 
 	return res
 }
+
+pub fn (x u64) hex() string {
+	res := ''
+	#res.str = x.val.toString(16)
+
+	return res
+}
+
+pub fn (x i64) hex() string {
+	res := ''
+	#res.str = x.val.toString(16)
+
+	return res
+}
+
+pub fn (x u32) hex() string {
+	res := ''
+	#res.str = x.val.toString(16)
+
+	return res
+}
+
+pub fn (x u16) hex() string {
+	res := ''
+	#res.str = x.val.toString(16)
+
+	return res
+}
+
+pub fn (x i8) hex() string {
+	res := ''
+	#res.str = x.val.toString(16)
+
+	return res
+}
+
+pub fn (x i16) hex() string {
+	res := ''
+	#res.str = x.val.toString(16)
+
+	return res
+}
+
+pub fn (x int) hex() string {
+	res := ''
+	#res.str = x.val.toString(16)
+
+	return res
+}
+
+pub fn (x int_literal) hex() string {
+	res := ''
+	#res.str = x.val.toString(16)
+
+	return res
+}
+
+pub fn (x byte) hex() string {
+	res := ''
+	#res.str = x.val.toString(16)
+
+	return res
+}
+
+// hex returns a string with the hexadecimal representation
+// of the byte elements of the array.
+pub fn (b []byte) hex() string {
+	mut hex := ''
+	for i in b {
+		mut z := i
+		z = z
+		#let n0 = i.val >> 4
+		#hex.str += n0 < 10 ? String.fromCharCode(n0) : String.fromCharCode(n0 + 87)
+
+		#let n1 = i.val & 0xF
+		#hex.str += n1 < 10 ? String.fromCharCode(n1) : String.fromCharCode(n1 + 87)
+	}
+	return hex
+}