Content Scope Runner: Difference between revisions

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An extension of the [[Content Script Injection]] technique, this snippet automatically runs the ''entire'' user script in the content scope.
As of Greasemonkey 1.0 specifying <code>[[@grant]] none</code> provides the behavior previously available by this technique.


<pre class="sample">if ('undefined' == typeof __PAGE_SCOPE_RUN__) {
The previous content of this page is available [http://wiki.greasespot.net/index.php?title=Content_Scope_Runner&oldid=7215 via history] only.
  (function page_scope_runner() {
    // If we're _not_ already running in the page, grab the full source
    // of this script.
    var my_src = "(" + page_scope_runner.caller.toString() + ")();";
 
    // Create a script node holding this script, plus a marker that lets us
    // know we are running in the page scope (not the Greasemonkey sandbox).
    // Note that we are intentionally *not* scope-wrapping here.
    var script = document.createElement('script');
    script.setAttribute("type", "application/javascript");
    script.textContent = "var __PAGE_SCOPE_RUN__ = true;\n" + my_src;
 
    script.setAttribute("src",
        "data:application/javascript,"+escape("var __PAGE_SCOPE_RUN__ = true;\n" + my_src));
 
    // Insert the script node into the page, so it will run, and immediately
    // remove it to clean up. Use setTimeout to force execution "outside" of
    // the user script scope completely.
    setTimeout(function() {
          document.body.appendChild(script);
          document.body.removeChild(script);
        }, 0);
  })();
 
  // Stop running, because we know Greasemonkey actually runs us in
  // an anonymous wrapper. Generates a warning w/ Scriptish?
  return;
}</pre>
 
As soon as execution reaches this code, the entire script will be injected into the page and re-run.
Thus you need not worry about any of the [[security]] restrictions from [[XPCNativeWrappers]] in the Greasemonkey [[sandbox]].
You also will, of course, not have access to any of the [[API]]s.
 
Google Chrome (last tested with Chrome 14) has problems with script tags with data URIs for the script tag's src attribute (see history for this Wiki page).
Instead, set the script tag's content as above.
 
== Tips ==
 
* This code must not be wrapped in a function, or the <code>return</code> will fail to work. It may be wrapped in a conditional.
* Any code before (and including) this block will be run twice: Once in GreaseMonkey context, once in page context.
* Any code after this block will only be run once, in the page context.
* You should change __PAGE_SCOPE_RUN__ to another identifier not present in web pages you run on and unique to your script, or only one of potentially multiple scripts the user has installed running on the current page will actually run.
 
== Explanation ==
 
The code block first checks to see if it is being run inside the page by looking for a marker it knows about.
If the marker is not present, the block creates and injects a script element that starts by setting the aforementioned marker variable and finishes by executing the text of the user script.
Finally, the block calls <code>return</code>, ending execution.
 
== @require ==
 
Since it must run before the rest of the script, this snipped functions best as the first [[Metadata Block#.40require|@require]].
Try it by adding this line as the first @require in the [[Metadata Block]]:
 
<nowiki>// @require http://userscripts.org/scripts/source/68059.user.js</nowiki>
 
[[Category:Coding Tips:Interacting With The Page]]
[[Category:@require Library]]

Latest revision as of 15:12, 23 September 2015

As of Greasemonkey 1.0 specifying @grant none provides the behavior previously available by this technique.

The previous content of this page is available via history only.