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

vlib/readline/readline_js.js.v

@@ -0,0 +1,32 @@
+module readline
+
+#const $readline = require('readline')
+
+struct Termios {}
+
+// Only use standard os.get_line
+// Need implementation for readline capabilities
+//
+// read_line_utf8 blocks execution in a loop and awaits user input
+// characters from a terminal until `EOF` or `Enter` key is encountered
+// in the input stream.
+// read_line_utf8 returns the complete input line as an UTF-8 encoded `[]rune` or
+// an error if the line is empty.
+// The `prompt` `string` is output as a prefix text for the input capturing.
+// read_line_utf8 is the main method of the `readline` module and `Readline` struct.
+
+pub fn (mut r Readline) read_line(prompt string) ?string {
+	res := ''
+	print(prompt)
+	#const rl = $readline.createInterface({input: $process.stdin,output: $process.stdout,prompt: prompt.str})
+	#rl.prompt()
+	#rl.on('line', function (ans) { rl.prompt(); res.str = ans; rl.close();})
+
+	return res
+}
+
+pub fn read_line(prompt string) ?string {
+	mut r := Readline{}
+	s := r.read_line(prompt) ?
+	return s
+}