How to parse a XML string in a Firefox addon using Add-on SDK

Question

I am trying to create a FF AddOn that brings some XML data from a website. But I can't find a way to parse my RESPONSE. First I used DOMParser but I get this error:

ReferenceError: DOMParser is not defined.

Someone suggested to use XMLHttpRequest, because the parsing is done automatically but then I get this other error:

Error: An exception occurred. Traceback (most recent call last):
File "resource://jid0-a23vmnhgidl8wlymvolsst4ca98-at-jetpack/api-utils/lib/cuddlefish.js", line 208, in require let module, manifest = this.manifest[base], requirer = this.modules[base]; TypeError: this.manifest is undefined

I really don't know what else to do. I must note that I am using the AddOn Builder to achieve this.

Below the code that doesn't seem to work.

Option 1:

exports.main = function() {

require("widget").Widget({
    id: "widgetID1",
    label: "My Mozilla Widget",
    contentURL: "http://www.mozilla.org/favicon.ico",
    onClick: function(event) {

    var Request = require("request").Request;
    var goblecontent = Request({
      url: "http://www.myexperiment.org/search.xml?query=goble",
      onComplete: function (response) {
        var parser = new DOMParser(); 
        var xml = parser.parseFromString(response.text, "application/xml");  

        var packs = xml.getElementsByTagName("packs");
        console.log(packs);
      }
    });

    goblecontent.get();

    }
});

};

Option 2:

exports.main = function() {
    require("widget").Widget({
        id: "widgetID1",
        label: "My Mozilla Widget",
        contentURL: "http://www.mozilla.org/favicon.ico",
        onClick: function(event) {

            var request = new require("xhr").XMLHttpRequest();
            request.open("GET", "http://www.myexperiment.org/search.xml?query=goble", false);
            request.send(null);  

            if (request.status === 200) {  
              console.log(request.responseText);  
            }  
        }
    });
};

score 14 · Accepted Answer · edited Apr 23 '13 at 18:04

14

DOMParser constructor isn't defined in the context of SDK modules. You can still get it using chrome authority however:

var {Cc, Ci} = require("chrome");
var parser = Cc["@mozilla.org/xmlextras/domparser;1"].createInstance(Ci.nsIDOMParser);

nsIDOMParser documentation.

That said, your approach with XMLHttpRequest should work as well. You used the new operator incorrectly however, the way you wrote it a new "require object" is being created. This way it should work however:

var {XMLHttpRequest} = require("xhr");
var request = new XMLHttpRequest();

Please consider using an asynchronous XMLHttpRequest object however, use request.onreadystatechange to attach your listener (the xhr module currently doesn't support other types of listeners or addEventListener).

edited Apr 23 '13 at 18:04

Paul Fournel

10,807
9
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answered Feb 07 '12 at 08:18

Wladimir Palant

56,865
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1

+1 for the sake of your users please avoid synchronous network access of any kind! – therealjeffg Feb 07 '12 at 13:25
@canuckistani: Now if only `xhr` implemented proper `onload` and `onevent` properties ;) Web developers might be used to `onreadystatechange` but I consider it an ugly solution. – Wladimir Palant Feb 07 '12 at 14:12
@Wladimir Palant. The DOMParse solution worked great. However the XMLHttpRequest solution threw at me the same error message. I ended up doing something similar to what you recommended me with DOMParse: `var {Cc, Ci} = require("chrome"); var request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Ci.nsIXMLHttpRequest);` and it worked!. Thank you – kriztean Feb 07 '12 at 16:03
@user1042066: Please don't do this. `xhr` module makes sure that the request is automatically aborted if your extension is uninstalled/disabled - the regular `XMLHttpRequest` won't do anything like this. – Wladimir Palant Feb 07 '12 at 16:07
@Wladimir Palant . I won't do that sorry. I found my mistake I copied the code you posted blindly without removing the `new` operator. Now it worked! thank you – kriztean Feb 07 '12 at 16:19
@kriztean: Ouch... You are right, the SDK consistently uses factory functions instead of the `new` operator and I completely missed that. Fixed my answer now. – Wladimir Palant Feb 07 '12 at 20:48
From the [xhr module docs](https://addons.mozilla.org/en-US/developers/docs/sdk/latest/packages/api-utils/xhr.html): _XMLHttpRequest(): Creates an XMLHttpRequest. This is a constructor, so its use should always be preceded by the new operator._ I have tested it and for me it doens't work if I don't use the new keyword. I get a _TypeError: null is not extensible_ error in xhr.js _this._req = req_. So correct way: `var xhr = require("xhr"); var req = new xhr.XMLHttpRequest();` – cprcrack Oct 26 '12 at 13:12
1

@cprcrack: You are right, I fixed the code. I think that this changed since the answer was written (it's an internal API so it can change at any time). – Wladimir Palant Oct 26 '12 at 22:15

score 3 · Answer 2 · answered Oct 26 '12 at 15:00

If you use XMLHttpRequest (available via the xhr module) you can easily avoid the use of DOMParser. Bellow I provide an example supposing request is an XMLHttpRequest object which request is successfully completed:

Instead of:

var parser = new DOMParser(); 
var xmlDoc = parser.parseFromString(request.responseText, "application/xml");

Use:

var xmlDoc = request.responseXML;

An then you can:

var packs = xmlDoc.getElementsByTagName("packs");
console.log(packs);

Or whatever.

on `responseXML` can you do `xmlDoc.document.body.innerHTML` like you could with `DOMParser`? — Noitidart, Nov 15 '14 at 07:33

How to parse a XML string in a Firefox addon using Add-on SDK

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