js: fix string.bytes codegen, readline, add tests for strings (#12060)

vlib/builtin/js/array.js.v

@@ -45,9 +45,9 @@ fn (mut a array_buffer) set(ix int, val voidptr) {
 #array_buffer.prototype.set = function(ix,val) { array_buffer_set(this,ix,val); }
 
 struct array {
-mut:
+pub mut:
 	arr array_buffer
-pub:
+
 	len int
 	cap int
 }
@@ -67,6 +67,14 @@ fn v_sort(mut arr array, comparator fn (voidptr, voidptr) int) {
 	}
 }
 
+// trim trims the array length to "index" without modifying the allocated data. If "index" is greater
+// than len nothing will be changed.
+pub fn (mut a array) trim(index int) {
+	if index < a.len {
+		a.len = index
+	}
+}
+
 #function flatIntoArray(target, source, sourceLength, targetIndex, depth) {
 #"use strict";
 #
@@ -368,7 +376,7 @@ pub fn (a &array) free() {
 // todo: once (a []byte) will work rewrite this
 pub fn (a array) bytestr() string {
 	res := ''
-	#a.arr.arr.forEach((item) => res.str += String.fromCharCode(+item))
+	#for (let i = 0;i < a.arr.len.valueOf();i++) res.str += String.fromCharCode(a.arr.get(new int(i)))
 
 	return res
 }

vlib/builtin/js/string.js.v

@@ -71,7 +71,7 @@ pub fn (s string) split(dot string) []string {
 pub fn (s string) bytes() []byte {
 	sep := ''
 	mut arr := s.str.split(sep.str).map(it.charCodeAt(0))
-	#arr = new array(arr)
+	#arr = new array(new array_buffer({arr,index_start: new int(0),len: new int(arr.length)}))
 
 	return arr
 }
@@ -735,11 +735,21 @@ pub fn (s string) index_after(p string, start int) int {
 
 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);
-	#})
-
+	if s.len == 0 {
+		return res
+	}
+	mut start := 0
+	mut end := 0
+	for i := 0; i < s.len; i++ {
+		if s[i] == 10 {
+			end = if i > 0 && s[i - 1] == 13 { i - 1 } else { i }
+			res << if start == end { '' } else { s[start..end] }
+			start = i + 1
+		}
+	}
+	if start < s.len {
+		res << s[start..]
+	}
 	return res
 }