onreadystatechange

状態が変化した時に発生するイベントです。

構文

オブジェクト.onreadystatechange = "イベント発生時の処理"

例文

<html>
 <head>
  <title>onreadystatechange</title>
  <script type="text/javascript"><!--
  function loadTextFile() {
   httpObj = createXMLHttpRequest(displayData);
   if (httpObj) {
    httpObj.open("get","data.txt",true);
    httpObj.send(null);
   }
  }
  function displayData() {
   if ((httpObj.readyState == 4) && (httpObj.status == 200)) {
    document.getElementById("result").value = httpObj.responseText;
   }
  }
// HTTP通信用、共通関数
  function createXMLHttpRequest(cbFunc) {
   var XMLhttpObject = null;
   try{  XMLhttpObject = new XMLHttpRequest();
   }catch(e){
    try{ XMLhttpObject = new ActiveXObject("Msxml2.XMLHTTP");
    }catch(e){
     try{ XMLhttpObject = new ActiveXObject("Microsoft.XMLHTTP");
     }catch(e){ return null; }
    }
   }
   if (XMLhttpObject) XMLhttpObject.onreadystatechange = cbFunc;
   return XMLhttpObject;
  }
 // --></script>
 </head>
 <body>
 <h1>onReadyState Change</h1>
 <form name="ajaxForm">
  <input type="button" value="読み込み" onClick="loadTextFile()"><br>
  <textarea name="result" cols="40" rows="5" id="result"></textarea>
 </form>
 </body>
</html>