Getting a value from a text file

**cmatkin** · 12-13-2005, 09:00 PM

Hi
I have a text file (values.txt) that contains information in the form of

A1=99
A2=3
A3=255
…
A454=23

I was wondering if there was a script that I can have on my html page that returns the value of the variable pointed to.

Eg:
A1 = getvalue(A1)

Regards
Craig

**jscheuer1** · 12-14-2005, 06:21 AM

Here is a little demo you might find interesting. There may be more efficient methods and I am not sure how this will react with large data files, hopefully someone with a clue on that will contribute to this thread. Also, since you say you already have this big file with the values in it, you could test it out on that and see how much lag time there is with a large file being parsed for individual values. For the purposes of this demo, I created data.txt and get_data.htm -

data.txt
------------------------

A1=99
A2=3
A3=255

------------------------

get_data.htm
------------------------

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
<html>
<head>
<title>Get Data - Demo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script type="text/javascript">
function getFile(filename)
  { oxmlhttp = null;
    try
      { oxmlhttp = new XMLHttpRequest();
        oxmlhttp.overrideMimeType("text/xml");
      }
    catch(e)
      { try
          { oxmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
          }
        catch(e)
          { return null;
          }
      }
    if(!oxmlhttp) return null;
    try
      { oxmlhttp.open("GET",filename,false);
        oxmlhttp.send(null);
      }
    catch(e)
      { return null;
      }
    return oxmlhttp.responseText;
  }

function getData(file, param){
return getFile(file).split(param+'=', 2)[1].split('\n', 1)[0]
}

</script>
</head>
<body>
<input type="button" onclick="alert(getData('data.txt', 'A1'))" value="A1"><br>
<input type="button" onclick="alert(getData('data.txt', 'A2'))" value="A2"><br>
<input type="button" onclick="alert(getData('data.txt', 'A3'))" value="A3"><br>
</body>
</html>

**jscheuer1** · 12-14-2005, 07:30 AM

The function getData(file, param) might be more efficient (I'm thinking about 'on a large data file', again) like so:

Code:

function getData(file, param){
var re = new RegExp('\n|.*'+param+'=(.*)$|.*', 'gm')
return getFile(file).replace(re, '$1')
}

**Twey** · 12-14-2005, 02:26 PM

Code:

        catch(e)
          { return null;
          }
      }
    if(!oxmlhttp) return null;

You're repeating yourself :-\
That second "return null" will never be reached; if the object can't be created, you've already returned null in the catch block above.

**jscheuer1** · 12-14-2005, 05:12 PM

Originally Posted by Twey

That second "return null" will never be reached; if the object can't be created, you've already returned null in the catch block above.

If true, it will harm nothing. I didn't write the function that part of the code belongs to and I do not fully understand it. As a result, I cannot be certain if that bit may or may not be needed. Perhaps it is a fallback for things like a 404 or 403 response.

**Twey** · 12-14-2005, 05:22 PM

Ah, I see. It would be necessary were it in a seperate function.

Code:

function getFile(filename) {
  oxmlhttp = null;
  try {
    oxmlhttp = new XMLHttpRequest();
    oxmlhttp.overrideMimeType("text/xml");
  } catch(e) {
    try {
      oxmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    } catch(e) { return null; }
  }
  try {
    oxmlhttp.open("GET",filename,false);
    oxmlhttp.send(null);
  } catch(e) { return null; }
  return oxmlhttp.responseText;
}

**jscheuer1** · 12-14-2005, 05:46 PM

I was just testing out the getFile function and, as I believe Mike pointed out in an earlier thread, it doesn't handle a 404 too well. Also I couldn't get it to reach that part in the code that you (Twey) say is redundant. Nevertheless, it is serviceable for the purpose I used it for.

**Twey** · 12-14-2005, 07:22 PM

Code:

function getFile(filename) {
  oxmlhttp = null;
  try {
    oxmlhttp = new XMLHttpRequest();
    oxmlhttp.overrideMimeType("text/xml");
  } catch(e) {
    try {
      oxmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    } catch(e) { return null; }
  }
  try {
    oxmlhttp.open("GET",filename,false);
    if(oxmlhttp.status == 404) {
      window.alert("URL doesn't exist!  Please contact the webmaster.");
      return null;
    } else if((oxmlhttp.status != 200 /*Request OK*/) && (oxmlhttp.status != 304 /*Not modified, don't know if this will be needed, but better safe than sorry*/)) {
      window.alert("An error " + oxmlhttp.status + " has occurred!  Please alert the webmaster.");
      return null;
    }
    oxmlhttp.send(null);
  } catch(e) { return null; }
  return oxmlhttp.responseText;
}

Originally Posted by John

it doesn't handle a 404 too well.

Now she does

**cmatkin** · 12-14-2005, 11:35 PM

I would like to thank all of you that help with the code here.
Your code works like a treat.

Thanks again.
Regards
CA

**jscheuer1** · 12-15-2005, 05:58 AM

I decided that I didn't like this whole:

XMLHttpRequest()/ActiveXObject("Msxml2.XMLHTTP")

method because Opera didn't seem to like it. I went ahead and created an entirely different approach, using an iframe. I will test out Twey's neat looking code soon but, I am not too optimistic about its working in Opera. Here is my latest:

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
<html>
<head>
<title>Get Data Iframe- Demo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script type="text/javascript">

/*Get Data Iframe script- © John Davenport Scheuer
  as first seen in Dynamic Drive Forums
  http://www.dynamicdrive.com/forums
  user name: jscheuer1
  */

//set source for data file.  Use a plain text file with one name=value pair per line.
var datasrc='data.txt'

///////////////No Need to Edit Below/////////////////
if(document.getElementById)
document.write('<iframe name="source" id="data" src="'+datasrc+'" style="position:absolute;top:-1000px;left:-1000px;visibility:hidden;"></iframe>')

function getData(param){
if(!document.getElementById)
return;
var frameObj=document.getElementById('data');
// Local Error Check (IE and Mozilla):
if (typeof source.location.href!=='string'||source.location.href.indexOf(datasrc)==-1){
alert('file: "'+datasrc+'" Unavailable')
return false;
}
var dataSet=frameObj.contentDocument? frameObj.contentDocument.body : frameObj.Document.body
dataSet=dataSet.innerHTML
var re = new RegExp(param+' *=', 'gm')
// Remote Error Check (IE, Mozilla and Opera) (Opera Local Error Check, as well)
if (!re.test(dataSet)){
alert('file: "'+datasrc+'" Unavailable\nor\nvariable: "'+param+'" Undefined')
return false;
}
re=new RegExp('\r|\n|.*'+param+' *=(.*)$|.*', 'gm')
return dataSet.replace(re,'$1').replace(/\r|<\/[XMPpRrEe]*>/, '');
}

</script>
</head>
<body>
<input type="button" onclick="alert(getData('A1'))" value="A1"><br>
<input type="button" onclick="alert(getData('A2'))" value="A2"><br>
<input type="button" onclick="alert(getData('A3'))" value="A3"><br>
</body>
</html>

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