Variable not updating in firefox content script when using self.port.on

Question

I'm trying to update the version var and that's not working the way my mind thinks it should. For instance, when I do:

self.port.on("get-version", ver => { version = ver; alert(version); });

I get an alert with the version number, but the HTML is still 0.0.0, which I used to define the version variable at the beginning of the content script.

main.js

pageMod.PageMod({
    include: "https://na6.salesforce.com/500?fcf=00B8000000*",
    contentStyleFile: ["./css/salesforceoverlay.css"],
    contentScriptFile: ["./external/jquery/jquery-1.11.3.min.js", "./js/salesforceoverlay.js"],
    onAttach: function(worker) { worker.port.emit('get-version', self.version); }
});

content-script.js

var version = "0.0.0";
self.port.on("get-version", ver => { version = ver; alert(version); });


$("body").append("<div id='helpSection' class='overlay'>\
    <p><b>Salesforce Overlay: " + version + "</b>\

    //more paragraphs/text and such... 

    </p>\
</div>");

score 2 · Answer 1 · answered Mar 04 '16 at 20:49

2

You're only updating the variable, not anything that has been derived in the past from that variable, i.e. the HTML contents.

This has nothing to do with FF addon code, it's a general propery of how HTML DOM and javascript in general works.

answered Mar 04 '16 at 20:49

the8472

40,999
5
70
122

So you're saying that the self.port.on is happening after the HTML has been appended; even though I have it before the jQuery function? That would explain everything... – japtain.cack Mar 04 '16 at 21:52

score -1 · Accepted Answer · answered Nov 24 '16 at 00:07

-1

Javascript promises were the answer. I have since re-written this to the current web-extensions format so the code is gone, but the issue was with synchronous/asynchronous code. Javascript promises fixed my issue by forcing synchronous behaviour.

answered Nov 24 '16 at 00:07

japtain.cack

131
11

Promises *do not* force synchronous behavior. They provide different semantics for asynchronous programming. The issue in your original code was that you were completely ignoring the asynchronous nature of inter-process messaging (messaging between background scripts and content scripts). Given this answer, I strongly recommend that you read the duplicate question, and [How do I return the response from an asynchronous call?](http://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) – Makyen Nov 27 '16 at 05:59

Variable not updating in firefox content script when using self.port.on

2 Answers2