W3Schools 在线编辑工具 V3.0

<html>
<body>

<script type="text/javascript">

var str="Hello world!"
document.write("The Unicode for the first character is: " + str.charCodeAt(0) + "<br />")
document.write("The Unicode for the second character is: " + str.charCodeAt(1) + "<br />")
document.write("The Unicode for the third character is: " + str.charCodeAt(2))

</script>

</body>
</html>

W3Schools 在线编辑工具（TIY） V3.0