Ajax ,XML and browsers

Alexandro · 12-13-2006, 01:38 PM

I have 2 problems:

1.IE, XML and Space

I need to parse something with java script.The problem is how internet explorer understand space?Un example:

Code:

<Li>
  <index>Li_j</index> 
  <name>Lithium</name> 
  <atomic_number>3</atomic_number> 
  <relative_atomic_mass>6.941000</relative_atomic_mass> 
  <melting_point>180.539993</melting_point> 
  <boiling_point>1342.000000</boiling_point> 
  <density>0.530000</density> 
  <covalent_radius>1.230000</covalent_radius> 
  <atomic_radius>2.050000</atomic_radius> 
  <atomic_volume>13.100000</atomic_volume> 
  </Li>
<Na>
  <index>Li_j</index> 
  <name>Lithium</name> 
  <atomic_number>3</atomic_number> 
  <relative_atomic_mass> </relative_atomic_mass> 
  <melting_point> </melting_point> 
  <boiling_point>1342.000000</boiling_point> 
  <density>0.530000</density> 
  <covalent_radius>1.230000</covalent_radius> 
  <atomic_radius>2.050000</atomic_radius> 
  <atomic_volume>13.100000</atomic_volume> 
  </Na>

Look at the bold code.When I parse I need to parse a space.
I select a radio button and put in a div : 180.539993 the value for melting point from Li.When I select another radio button I need to put in the same div a space, but is not doing to do that, it keep the previous and give me a java script error.
Yes I can put another value and tested and when I parse this value to put space instead in div, but I have to do many modifications to code and that is not realy a option.My question is what to put in the XML
<melting_point>SPACE</melting_point> that IE consider it a space?
I try to us the

Code:

 &#32 and &nbsp and &amp32

and is not working

2.Ajax and Browser Cache

When I request a particular web page, the browser first tries to load the page from its cache, rather than submitting a new HTTP request.

If I use a php url I wil use something like this

Code:

myRandom=parseInt(Math.random()*99999999);
myRequest.open("GET", url  + myRandom, true);

or I use the current timestamp

Code:

myRand= + new Date().getTime();

But the problem is I parse with java scripts text and xml files(url) not php and the trick above is not working with this kind of file.
I can add HTTP headers to the data returned by server-side routines, intended to tell the browser not to cache a particular page,but different browsers have different cache support different header declarations, making it difficult to ensure that pages are not cached.
I cant use "url mod rewrite" in apache because by hosting does not give me acces,
What I can do in this situation ?

StupidScript · 12-13-2006, 04:30 PM

Code:

&#32 and &nbsp and &amp32

should each have a semi-colon at the ends (i.e.   ).

About the caching problem, it looks like the request should be unique every time, so how is it that they are being drawn from the cache at all?

Alexandro · 12-13-2006, 05:12 PM

1.Well I use the semicolon ";" in XML, I just not writed in the post

2.I use Ajax so I only get and put data in the XML.I am not reload the all page like in php,it is the same page,url,sesion only some data,text is change.

All browsers maintain a so-called cache of visited web pages, a local record of page contents stored on the hard disk of the browser's computer. When you request a particular web page, the browser first tries to load the page from its cache, rather than submitting a new HTTP request.This appears to be more of a problem with IE and browser based on IE than with the non-Microsoft browsers. Only GET requests are affected; POST requests are not cached.
Why browsers do that, I dont know maybe we should ask Microsoft and the others.This is kind of s..t because every browser have a style to treat XML.

StupidScript · 12-13-2006, 05:46 PM

Re: space

Can you use some character string instead of a space, like "ggggg" and programmatically replace it with a space on rendering (i.e. PHP's str_replace("ggggg"," ",$xmloutput))?

Re: caching

Yes, thank you. The way the caching process is supposed to work is that the browser compares the timestamp of the page being requested with that of the one in its cache. If the page on the server is newer than the one in the cache, it's supposed to grab the new page. If they have the same timestamp, re-using the cached page saved a lot of bandwidth for dial-up users back in the day when 1200 baud was a kickass connection.

But, again, the code you posted (or something like it) should result in a unique request that would not have been matched by anything in the browser's cache due to your use of the randomizer, whether you used Javascript or PHP or whatever. What is your guess as to why it is being drawn from the cache in the first place? It's a "new", unique request.

If you are not requesting an actual page, but just some data, then why would the browser even cache the data in the first place? I suspect you _are_ requesting a page, even though the data contained in that page is dynamic.

Furthermore, piping that request through the XMLHttpRequest mechanism should remove any question in the browser's mind that the request must be gotten from the server each time. How are you implementing your AJAX request initialization?

Alexandro · 12-14-2006, 03:34 AM

The timestamp work if the url is a php script(file) but if i get a xml.file is not working;
I have 50 diferent elements in total 1000 elements in a for then in a switch, because the change are determined by user and it is a coding problem because I have to write for every switch a function specific.

StupidScript · 12-14-2006, 04:41 PM

What about making the request for a PHP page with various parameters and having the PHP generate the XML file that is returned? It doesn't need the .xml extension, as long as the headers are correct. It sounds like you are describing a problem with MSIE's recognizing a valid format or something like that.

Does this look like the XMLHttpRequest initialization you are using?

Code:

var http_request = false;
if (window.XMLHttpRequest) {
 http_request = new XMLHttpRequest();
 if (http_request.overrideMimeType) {
  http_request.overrideMimeType('text/xml');
 }
}
else if (window.ActiveXObject) {
 try {
  http_request = new ActiveXObject("Msxml2.XMLHTTP");
 } catch (e) {
  try {
   http_request = new ActiveXObject("Microsoft.XMLHTTP");
  } catch (e) {}
 }
}

You can use http_request.send("param1=value1&param2=value2"); to pass the parameters to the page you're GETting.

Alexandro · 12-14-2006, 04:58 PM

It is similar:

Code:

function gXMLHTTPRequest()
{
var req = false;
try
  {
    req = new XMLHttpRequest(); /* e.g. Firefox */
  }
catch(err1)
  {
  try
    {
     req = new ActiveXObject("Msxml2.XMLHTTP");
  /* some versions IE */
    }
  catch(err2)
    {
    try
      {
       req = new ActiveXObject("Microsoft.XMLHTTP");
  /* some versions IE */
      }
      catch(err3)
        {
         req = false;
        }
    }
  }
return req;
}

var myRequest = getXMLHTTPRequest();

but I resolved the problem because In my case I can use " - " instead of " ",
but for other aplications remains an option

StupidScript · 12-15-2006, 12:29 PM

Cool. So, using the hyphen instead of the space, does that just solve the space issue, or is it also helping with the caching issue?

Alexandro · 12-15-2006, 01:31 PM

With the white space only , but in other situation maybe I will be bound to use white space instead - so the question remains.