chrome.runtime.sendMessage raises "Uncaught TypeError: Cannot call method 'sendMessage' of undefined "

Question

I am writing a google chrome extension and trying to send information from a piece of code that is injected into a web page to my content script.

According to http://developer.chrome.com/extensions/messaging#external-webpage, I should use something like :

// 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);
  });

The problem is, when I do :

var script_code = "var msg = {message : 'plop'};\n";
script_code += "chrome.runtime.sendMessage('" + chrome.i18n.getMessage("@@extension_id") + "', msg, function(response) {\n";
script_code += "    console.log('response received');\n";
script_code += "});\n";

An then inject this to the webpage, when it is executed, I get :

Uncaught TypeError: Cannot call method 'sendMessage' of undefined

Can anyone help me through this ?

Thanks

Answer 1

javaScript code in Chrome extensions can be divided in the following groups:

• Extension code - Full access to all permitted chrome.* APIs.
  This includes all extension pages(background page, popup page ,option page, and so on)

• Content scripts (via the manifest file or chrome.tabs.executeScript) - Partial access to some of the chrome APIs
  Full access to the page's DOM.

• Injected scripts (via this method in a Content script) - Full access to all properties in the page. No access to any of the chrome. APIs.*
  Execute on the actual page, can't access any of the chrome.* APIs.**.

In your case, code is execute on the actual page, can't call chrome.runtime.* APIs.
Maybe, you can try window.postMessage().