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javascriptfirefoxgreasemonkeyuserscripts

document.write() not working in userscript with Firefox


I have some userscripts that use

var tab = window.open('', '_blank');
tab.document.write(myCustomHtml);
tab.document.close();

to show an output to the user (myCustomHtml being some valid HTML I defined previously in the code). It sopped working in Firefox since version 27, now I only get an empty document. No console errors whatsoever.

The newly opened document has only this content when inspected with Firefox' console

<html>
    <head></head>
    <body>
    </body>
</html>

while the source code is empty.

The code works in Chrome.

Do I need to make any modification for newer Firefox versions (27+) and an updated Greasemonkey (1.15)? I haven't found any recent bug reported to Firefox about this issue.

Here's a test script

// ==UserScript==
// @name           document.write() test
// @namespace      stackoverflow.com
// @description    tests document.write()
// @include        https://stackoverflow.com/questions/22651334/*
// @include        http://stackoverflow.com/questions/22651334/*
// @version        0.0.1
// ==/UserScript==

var tab = window.open('', '_blank');
tab.document.write('<html><head></head><body><ul><li>a</li><li>b</li><li>c</li></ul></body></html>');
tab.document.close();

Solution

  • I'm not sure if Greasemonkey or Firefox has buggered this, but window.open to a blank page, from a Greasemonkey script, now triggers a Same Origin Policy violation.
    Meanwhile, Page scope, the console scope, and Firebug's console all work fine.

    Greasemonkey scope gives:

    SecurityError: The operation is insecure

    whether @grant none is used or not.

    This, plus the general uselessness of GM_openInTab(), lead me to suspect it is a Greasemonkey bug. I don't have time to look into it right now, but file a bug report, if you wish.

    To get this to work on the latest release of Firefox (28.0) and Greasemonkey (1.15), here's what I had to do:

    1. Tell my popup blockers to (temporarily) allow popups from stackoverflow.com.
    2. Inject the popup code into the page scope.
    3. Use an explicit about:blank for the URL.
    4. Wait for the new window to load.

    Here's a complete script that works on the latest FF+GM releases:

    // ==UserScript==
    // @name        document.write () test
    // @description tests document.write ()
    // @include     http://stackoverflow.com/questions/22651334/*
    // ==/UserScript==
    
    function fireNewTab () {
        var newTab = window.open ('about:blank', '_blank');
        newTab.addEventListener (
            "load",
            function () {
                //--- Now process the popup/tab, as desired.
                var destDoc = newTab.document;
                destDoc.open ();
                destDoc.write ('<html><head></head><body><ul><li>a</li><li>b</li><li>c</li></ul></body></html>');
                destDoc.close ();
            },
            false
        );
    }
    
    addJS_Node (null, null, fireNewTab);
    
    function addJS_Node (text, s_URL, funcToRun, runOnLoad) {
        var D                                   = document;
        var scriptNode                          = D.createElement ('script');
        if (runOnLoad) {
            scriptNode.addEventListener ("load", runOnLoad, false);
        }
        scriptNode.type                         = "text/javascript";
        if (text)       scriptNode.textContent  = text;
        if (s_URL)      scriptNode.src          = s_URL;
        if (funcToRun)  scriptNode.textContent  = '(' + funcToRun.toString() + ')()';
    
        var targ = D.getElementsByTagName ('head')[0] || D.body || D.documentElement;
        targ.appendChild (scriptNode);
    }