Call background function of Chrome extension from a site

Question

I am looking for a function inside a webpage te activate a chrome extension.

Imagine that http://www.example.com/test.html contains:

Answer 1

There is a builtin solution to Send messages from web pages to the extension

mainfest.json

"externally_connectable": {
  "matches": ["*://*.example.com/*"]
}

Web page:

// The ID of the extension we want to talk to.
var editorExtensionId = "abcdefghijklmnoabcdefhijklmnoabc";

// Make a simple request:
chrome.runtime.sendMessage(editorExtensionId, {openUrlInEditor: url},
  function(response) {
    if (!response.success)
      handleError(url);
  });

Extension's background script:

chrome.runtime.onMessageExternal.addListener(
  function(request, sender, sendResponse) {
    if (sender.url == blacklistedWebsite)
      return;  // don't allow this web page access
    if (request.openUrlInEditor)
      openUrl(request.openUrlInEditor);
  });