javascript.dohow.jp
<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="UTF-8">
<title>JavaScriptの練習</title>
</head>
<body>
<script type="text/javascript">
<!--
function getBytes(strSrc){
var len = 0;
strSrc = escape(strSrc);
for(i = 0; i < strSrc.length; i++, len++){
if(strSrc.charAt(i) == "%"){
if(strSrc.charAt(++i) == "u"){
i += 3;
len++;
}
i++;
}
}
return len;
}
// -->
</script>
<form name="myForm">
<input name="text1" type="text" id="text1" size="40">
<input type="button" onClick="alert(getBytes(document.myForm.text1.value));" value="バイト数は?">
<form>
</body>
</html>