数字、大小写字母的字符编码

<script>
    var html=""
    for(var i=48;i<58;i++){
        html+=i+":"+String.fromCharCode(i)+"\n"
    }
    for(var i=65;i<91;i++){
        html+=i+":"+String.fromCharCode(i)+"\n"
    }
    for(var i=97;i<123;i++){
        html+=i+":"+String.fromCharCode(i)+"\n"
    }
    document.write(html)
</script>
<script>
    var html=""
    for(var i=48;i