回答

<script type="text/javascript">
    function getFileSize(fileByte) {
        var fileSizeByte = fileByte;
        var fileSizeMsg = "";
        if (fileSizeByte < 1048576) fileSizeMsg = (fileSizeByte / 1024).toFixed(2) + "KB";
        else if (fileSizeByte == 1048576) fileSizeMsg = "1MB";
        else if (fileSizeByte > 1048576 && fileSizeByte < 1073741824) fileSizeMsg = (fileSizeByte / (1024 * 1024)).toFixed(2) + "MB";
        else if (fileSizeByte > 1048576 && fileSizeByte == 1073741824) fileSizeMsg = "1GB";
        else if (fileSizeByte > 1073741824 && fileSizeByte < 1099511627776) fileSizeMsg = (fileSizeByte / (1024 * 1024 * 1024)).toFixed(2) + "GB";
        else fileSizeMsg = "文件超过1TB";
        return fileSizeMsg;
    }
    alert(getFileSize(123123213));
</script>