This is a web page for testing the kind of access content scripts get to the web pages they run inside.
+The page includes a page script, which does three things:
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Adds a new paragraph, with code like this:
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+var p = document.createElement("p");
+p.textContent = "This paragraph was added by a page script.";
+p.setAttribute("id", "page-script-para");
+document.body.appendChild(p);
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Adds a new variable "foo" to the global window object, with code like this:
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+window.foo = "This global variable was added by a page script";
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redefines the build-in window.confirm() function, with code like this:
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+window.confirm = function() {
+ alert("The page script has also redefined 'confirm'");
+}
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If you now install the content-scripts extension, and reload the page, you'll now see two columns of buttons underneath this text.
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Each column contains three buttons:
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Button 1 toggles a blue background for the paragraph the page script added.
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Button 2 prints the value of "window.foo" in the text box below.
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Button 3 calls window.confirm()
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The exact same code is running in each column. But the left-hand column is running in the page script, while the right-hand button is running in the content script. So you'll see the following:
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Button 1 gives the same result in both columns: content scripts can see and modify the DOM, even for elements added by page scripts.
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Button 2 gives "undefined" for the content script column: content scripts can't see variables added by page scripts.
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Button 3 calls the original, unmodified version of window.confirm(): content scripts are unaffected by redefinitions of built-in DOM functions that are made by page scripts.
Clicking one button sends a message from the page script to the content script: the content script just displays an alert when it receives the message. Clicking the other button sends a message the other way.