file exists function available?

[jmrker]

I am using the code below to load a text file from the server into a <textarea> of the HTML.

Is there a function that checks if the filename was found?
Currently, it fills the textarea with a 'file not found' HTML page.
What I would like to know is if the file was found before I load in the garbage information.

function el(tid) { return document.getElementById(tid); }

var myAjax = {
  TextInformation : '',
// From: http://codingforums.com/showthread.php?t=143412&highlight=file
  myAjaxIO : function (U, V) { //LA MOD String Version. A tiny ajax library.  by, DanDavis
    var X = !window.XMLHttpRequest 
	  ? new ActiveXObject('Microsoft.XMLHTTP') 
	  : new XMLHttpRequest();
    X.open(V ? 'PUT' : 'GET', U, false );
    X.setRequestHeader('Content-Type', 'text/html');
    X.send(V ? V : '');
    return X.responseText;
  },
  doLoad : function (filename) { this.TextInformation = this.myAjaxIO(filename); },
  getTextInfo : function () { // alert(this.TextInformation);  // for testing purposes
    return this.TextInformation }
}

function Load_and_Show(filename) {
  myAjax.doLoad(filename);
  el('TArea').value=myAjax.getTextInfo();
}

[Dormilich]

make an AJAX HEAD* call and check the status code (i.e. 200/404).



* - like GET, but only headers are sent back.

[jmrker]

Originally Posted by Dormilich

make an AJAX HEAD* call and check the status code (i.e. 200/404).



* - like GET, but only headers are sent back.

Thanks - I'll google that and look into it.
I just did not know the words to look for in my search.

[jmrker]

Could you take a peek at this?

Error console says "XMLHttp is not defined".
I've also tried "xmlhttp", if that matters, with similar results.

var myAjax = {
  TextInformation : '',
// From: http://codingforums.com/showthread.php?t=143412&highlight=file
  myAjaxIO : function (U, V) { //LA MOD String Version. A tiny ajax library.  by, DanDavis
    var X = !window.XMLHttpRequest 
	  ? new ActiveXObject('Microsoft.XMLHTTP') 
	  : new XMLHttpRequest();
    X.open(V ? 'PUT' : 'GET', U, false );
    X.setRequestHeader('Content-Type', 'text/html');
    X.send(V ? V : '');
    return X.responseText;
  },

  exists : function (filename) {
    var fileStatus = false;
    XMLHttp.open("HEAD",filename,true);
    XMLHttp.onreadystatechange=function() {
      if (XMLHttp.readyState==4) {
       if (XMLHttp.status==200) fileStatus = true   // alert("URL Exists!")
       else if (XMLHttp.status==404) fileStatus = false   // alert("URL doesn't exist!")
            else alert("Status is "+XMLHttp.status)
      }
    }
    XMLHttp.send(fileStatus)		//  xmlhttp.send(null)
  },

  doLoad : function (filename) { this.TextInformation = this.myAjaxIO(filename); },
  getTextInfo : function () { // alert(this.TextInformation);  // for testing purposes
    return this.TextInformation }
}

function Load_and_Show(filename) {
  if (myAjax.exists(filename)) {
    myAjax.doLoad(filename);
    el('TArea').value=myAjax.getTextInfo();
  } else { alert(filename+' does not exist'); }
}

[jmrker]

Changed to the following and all seems OK now.

var myAjax = {
  TextInformation : '',
// From: http://codingforums.com/showthread.php?t=143412&highlight=file
  myAjaxIO : function (U, V) { //LA MOD String Version. A tiny ajax library.  by, DanDavis
    var X = !window.XMLHttpRequest 
	  ? new ActiveXObject('Microsoft.XMLHTTP') 
	  : new XMLHttpRequest();
    X.open(V ? 'PUT' : 'GET', U, false );
    X.setRequestHeader('Content-Type', 'text/html');
    X.send(V ? V : '');
    return X.responseText;
  },

  exists : function(url) {
    var http = new XMLHttpRequest();
    http.open('HEAD', url, false);
    http.send();
    return http.status!=404;
  },

  doLoad : function (filename) { this.TextInformation = this.myAjaxIO(filename); },
  getTextInfo : function () { // alert(this.TextInformation);  // for testing purposes
    return this.TextInformation }
}
function Load_and_Show(filename) {
  if (myAjax.exists(filename)) {
    myAjax.doLoad(filename);
    el('TArea').value=myAjax.getTextInfo();
  } else { alert(filename+' does not exist'); }

}