Function won't repeat

**kasei** · 12-29-2007, 05:40 PM

I'm trying to get this function to repeat once every second.

It's supposed to:
1. copy the text off of the webpage
2. split it at the '|'
3. add the second string to the document
4. replace the variable in the function's bracket with the first string from the split
5. and repeat the process after 1000 miliseconds.

Code:

function getPage(t) {
var xmlhttp=false;
        try {
                xmlhttp = new ActiveXObject('Msxml2.XMLHTTP');
        } catch (e) {
                try {
                        xmlhttp = new
                        ActiveXObject('Microsoft.XMLHTTP');
            } catch (E) {
                xmlhttp = false;
                        }
        }
        if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
                xmlhttp = new XMLHttpRequest();
        }

        var file = 'http://webpage.com/page.php?t=';
    xmlhttp.open('GET', file + t, true);
    xmlhttp.onreadystatechange=function() {
        if (xmlhttp.readyState==4) {
                var content = xmlhttp.responseText;
                var bit = content.split("|");
                document.getElementById('text').innerHTML += bit[1];
        }
        }
        xmlhttp.send(null);
return;
r=setTimeout("getPage(bit[0])",1000);
}

Everything seems to work fine until it's time to repeat. Then I get an error that says 't' is undefined

**Trinithis** · 12-29-2007, 06:44 PM

You need to place the return statement after the timeout.

**tech_support** · 12-30-2007, 12:46 AM

And bit[0] needs to be outside of the string, like this:

Code:

r=setTimeout("getPage('"+bit[0]+"')",1000);

**jscheuer1** · 12-30-2007, 12:54 AM

Or, the way real coders do it:

Code:

r=setTimeout(function(){getPage(bit[0]);},1000);

What's r?

**Twey** · 12-30-2007, 03:00 AM

Or, the way real coders do it:

Or sane people.

What's r?

A numerical identifier for the timeout request (used with clearTimeout() &c.).

Neither of these solutions will work, of course, because "bit" is local to the onchange function.

Code:

var Xhr = (function() {
  var xhr = null;

  function newXhr() {
    if(window.XMLHttpRequest)
      return new XMLHttpRequest();
    else if(window.ActiveXObject)
      try {
        return new ActiveXObject("Msxml2.XMLHTTP");
      } catch(e) {
        return new ActiveXObject("Microsoft.XMLHTTP");
      }
    return null;
  }

  function getXhr() {
    return xhr || (xhr = newXhr());
  }

  function getFile(url, callback) {
    var xhr = getXhr();
    xhr.open("GET", url, !!callback);
    if(callback)
      xhr.onreadystatechange = function() {
        if(this.readyState === 4)
          return callback(this.responseText);
      };
    xhr.send(null);
    return callback ? undefined : xhr.responseText;
  }

  return {
    newXhr: newXhr,
    getXhr: getXhr,
    getFile: getFile
  };
})();

// I'm not sure what this function should be called, but
// "getPage" is woefully inaccurate.
function awakenLateParrot(t) {
  Xhr.getFile("http://webpage.com/page.php" + (t ? "?t=" + t : ""),
    function(text) {
      // Hurry up o ye days of destructuring assignment and
      // (nextT, toAppend) = text.split("|"); // :-(
      var nextT = text.split("|"),
        toAppend = nextT[1];
      nextT = nextT[0];

      document.getElementById("text").appendChild(document.createTextNode(toAppend));
      setTimeout(function() { awakenLateParrot(nextT); }, 1000);
    });
}

**Trinithis** · 12-30-2007, 03:22 AM

A numerical identifier for the timeout request (used with clearTimeout() &c.).

Numerical? Don't you mean alphabetic?

**Twey** · 12-30-2007, 03:35 AM

No, numerical. It's an integer.

**jscheuer1** · 12-30-2007, 04:15 AM

Yes, r would be a number, but it is undeclared and in the global scope, so it's an error waiting to happen. I asked what it was to get at that fact, not because I didn't know what sort of value it would (if unencumbered by errors) be assigned.

**kasei** · 12-30-2007, 12:46 PM

Originally Posted by jscheuer1

What's r?

I don't know... I'm pretty weak on JavaScript, but I'm trying to learn. I just used what I saw on www.w3schools.com to see if I could splice it together and make it work.

Code:

<html>
<head>
<script type="text/javascript">
function timedMsg()
{
var t=setTimeout("alert('5 seconds!')",5000);
}
</script>
</head><body>
<form>
<input type="button" value="Display timed alertbox!"
onClick="timedMsg()">
</form>
</body>
</html>

In this case, I just took the function and replaced t (which is also undeclared, isn't it?) with r since I was already using t as a variable at the time.

Thank you Twey, that seems to fix that problem. Onto the next bug...

**kasei** · 12-30-2007, 01:51 PM

Well...

I don't get any more errors, but it doesn't display anything at all now!

Code:

<html>
<head>
<title>Test</title>

<script type="text/javascript">
var Xhr = (function() {
  var xhr = null;

  function newXhr() {
    if(window.XMLHttpRequest)
      return new XMLHttpRequest();
    else if(window.ActiveXObject)
      try {
        return new ActiveXObject("Msxml2.XMLHTTP");
      } catch(e) {
        return new ActiveXObject("Microsoft.XMLHTTP");
      }
    return null;
  }

  function getXhr() {
    return xhr || (xhr = newXhr());
  }

  function getFile(url, callback) {
    var xhr = getXhr();
    xhr.open("GET", url, !!callback);
    if(callback)
      xhr.onreadystatechange = function() {
        if(this.readyState === 4)
          return callback(this.responseText);
      };
    xhr.send(null);
    return callback ? undefined : xhr.responseText;
  }

  return {
    newXhr: newXhr,
    getXhr: getXhr,
    getFile: getFile
  };
})();

// I'm not sure what this function should be called, but
// "getPage" is woefully inaccurate.
function awakenLateParrot(t) {
  Xhr.getFile("http://test.game.joescuriosityshoppe.com/chat/getposts.php" + (t ? "?t=" + t : ""),
    function(text) {
      // Hurry up o ye days of destructuring assignment and
      // (nextT, toAppend) = text.split("|"); // :-(
      var nextT = text.split("|"),
        toAppend = nextT[1];
      nextT = nextT[0];

      document.getElementById("text").appendChild(document.createTextNode(toAppend));
      setTimeout(function() { awakenLateParrot(nextT); }, 1000);
    });
}
</script>

</head>
<body onload="awakenLateParrot('0')">
<div id="text"></div>
</body>
</html>

I've set getposts.php to display a 4 character number, followed by "|<div>hello</div>", no matter if t has any value at all.

If it worked, then "hello" should be displayed and the function should repeat after 1000 miliseconds with the 4 character number as the new t, right?

All I get is a blank screen.

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