/* main section */
view();

/* subroutine section */
function view()
{
    document.write(
        '<p>入力された文字列内の&amp;、&quot;、&lt;、&gt;を実体参照に変換します。変換はJavaScriptでおこなわれます。</p>'
       ,'<form id="inputdata" onsubmit="return encode(this)">'
       ,'<p><label for="str">文字列</label><br><textarea name="str" id="str" style="width:100%; height:4em"></textarea><br><input type="button" value="変換" onclick="encode(this.form)"></p>'
       ,'<p><label for="entities">変換結果</label><br><textarea name="convert_result"  id="entities" style="width:100%; height:4em"></textarea>'
       ,'</form>'
    );
}

function encode(formObj)
{
    var result = encodeEntities(formObj.str.value);
    formObj.convert_result.value = result;
    return false;
}

function convert_to_str()
{
}

function encodeEntities(value)
{
    value = value.replace(/&/g,"&amp;");
    value = value.replace(/</g,"&lt;");
    value = value.replace(/>/g,"&gt;");
    value = value.replace(/"/g,"&quot;");
    return value;
}