JavaScript variable scope

Peteee

I'm having a few troubles with a firefox extension I'm developing.

I have one function to download an XML file, and another to parse the XML file.

function getXML()
{
	
    XMLDOC = "";
    var req = new XMLHttpRequest();
    req.open( 'GET', 'http://www.xxx.xml', false );
    req.send( null );
    if( req.status == 200 )

      XMLDOC = req.responseText;
    
}

and

function getOther(){
    //Begining XML Parsing
    // initiate new DOMParser
    var parser = new DOMParser();
    // Load XMLDOC into a variable so it can be parsed
    var doc = parser.parseFromString( XMLDOC, "text/xml" );

etcetcetc

So when we run the getXML(), the XML file gets loaded into the XMLDOC variable. However when I run the getOther() function, Javascript complains that XMLDOC hasn't been defined (Even though it has been defined an initialised with values) in the above function.

Theres probably something really trivial that I'm missing here

Giblet

Shouldn't XMLDOC have var in front of it?

Peteee

Dosent matter, it complains about the same thing.

Creamy Goodness

i'm not great on the old javascript but aren't variables declared inside functions only able to be used inside that function?

to use a variable in other function you'll need to get the getXML() function to return the value you want and then pass it as a parameter into the getOther() function.

Evil Phil

Yeah, what Creamo said. Shouldn't XMLDOC be declared outside of getXML()?

i.e.

var XMLDOC = "";

function getXML()
{
   ...
}
function getOther()
{
   ...
}

NutJob

For it to work you need to declare XMLDOC somewhere

Then walk through the code with firebug and if theres anything else it'll highlight it

ron_darrell

The problem isn't with the declaration of the XMLDoc variable, it's with the fact that your function doesn't return a value and that the function getXML is not called before XMLDOC is used. If you try this instead it should work:

function getXML()
{

XMLDOC = "";
var req = new XMLHttpRequest();
req.open( 'GET', 'http://www.xxx.xml', false );
req.send( null );
if( req.status == 200 )

XMLDOC = req.responseText;
return XMLDOC;
}

Code:
function getOther(){
//Begining XML Parsing
// initiate new DOMParser
var parser = new DOMParser();
// Load XMLDOC into a variable so it can be parsed
var doc = parser.parseFromString( getXML(), "text/xml" );

etcetcetc

Otherwise you need to declare XMLDOC as a variable outside of the getXML and getOther functions and call getXML from inside getOther as follows:

var XMLDOC = "";
function getXML()
{

XMLDOC = "";
var req = new XMLHttpRequest();
req.open( 'GET', 'http://www.xxx.xml', false );
req.send( null );
if( req.status == 200 )

XMLDOC = req.responseText;

}

Code:
function getOther(){
//Begining XML Parsing
// initiate new DOMParser
var parser = new DOMParser();
// Load XMLDOC into a variable so it can be parsed
getXML();
var doc = parser.parseFromString( XMLDOC, "text/xml" );

etcetcetc

-RD

Peteee

Cremo wrote:

i'm not great on the old javascript but aren't variables declared inside functions only able to be used inside that function?

to use a variable in other function you'll need to get the getXML() function to return the value you want and then pass it as a parameter into the getOther() function.

As far as I know if there is no 'var' in front of it then you can access it from anywhere.

The getXML() is called before getOther() so it should be initialised before getXML() is called.

Shouldn't XMLDOC be declared outside of getXML()?

If I declare it as blank, then it will get wiped the next time the function runs. I want the contents of XMLDOC to be stored.

Since its a HTTP request I dont want to wait on the function everytime the script is run (i.e. every time a page is refreshed, I think JavaScript throws up an error about this too)

None of these solutions seems to have worked unfortunatly

Evil Phil

Peteee wrote:

If I declare it as blank, then it will get wiped the next time the function runs. I want the contents of XMLDOC to be stored.

Hmmm, what's the flow of the code here, are you trying to persist XMLDOC across a GET or a POST?

ron_darrell

Javascript isn't designed to persist variables across multiple pages or a get / post. Javascript is client browser based only and designed specifically to prevent the storing or writing of data to a client machine (though you can write data to cookies which is a possible work around)

Evil Phil

ron_darrell wrote:

Javascript isn't designed to persist variables across multiple pages or a get / post. Javascript is client browser based only and designed specifically to prevent the storing or writing of data to a client machine (though you can write data to cookies which is a possible work around)

Yeah, we know.

Peteee

ron_darrell wrote:

Javascript isn't designed to persist variables across multiple pages or a get / post. Javascript is client browser based only and designed specifically to prevent the storing or writing of data to a client machine (though you can write data to cookies which is a possible work around)

Yeah I figured that out I'm now writing the values to a temporary file in the users temp directory (Firefox allows this)

So I have the getXML() saving a file, and getCurrency() opening that file and reading them off into variables etc using(Huzzah!).

Another problem, since JavaScript dosent persist variables I need to load the values each time the script is run (i.e. on a new page load).

So I try to call the getOther() function (each time a page loads), but it throws a 'uncaught exception: Permission denied to get property UnNamedClass.class'

Googling this seems to imply some sort of cross-site-scripting vulnerability?

Peteee

Right, you can probably ignore all this. I just found out firefox extensions have a preferences 'thingy' for just this type of thing.

Should have researched better rather then trying to reinvent the wheel!

Thanks for all your help regardless!