Get value of an input element on a firefox addon

Question

How i can fetch the value of this input element in my main.js:

<input type="hidden" value="12124054" id="ctl00_cphContent_hdnID" name="ctl00$cphContent$hdnID">

I tried var id = document.getElementById("ctl00_cphContent_hdnPlayerID").value; and contentWindow.document.getElementById("ctl00_cphContent_hdnPlayerID").focus(); but i am getting errors that document and contentWindows are unidentified :(

Answer 1

You need to get the value from the page using a content script and then send the value to main.js - this is because web content is inherently untrusted by the addon-sdk. Please see these docs for more on how to use content scripts:

https://addons.mozilla.org/en-US/developers/docs/sdk/1.0/dev-guide/addon-development/web-content.html#content_script_events

Here is an example add-on on Builder that shows how to pass values frmo the content script back to main.js. In this case I'm using the xui library to more easily bind events in the pgae.