page-workr scraping example

main.js

let { Page } = require('sdk/page-worker');
let self = require('sdk/self');
let { ActionButton } = require("sdk/ui/button/action");

let worker = Page({
  contentScriptFile: [self.data.url('worker.js'), 
                      self.data.url('jquery.js')]
});

worker.on('fetched', function(data) {
  // do something with the data
});

// a basic button to trigger the fetch command.
let button = ActionButton({
    id: "my-button",
    label: "my button",
    icon: {
      "16": "./firefox-16.png",
      "32": "./firefox-32.png"
    },
    onClick: function(state) {
      worker.port.emit('fetch');
    }
  });

worker.js

$(function() {
  self.port.on('fetch', function() {
    // use jQuery to extract some data
    var something = $('.classname').html();
    // the data you send can only be arrays, text, numbers, not a whole jQuery result
    self.port.emit('fetched', something);
  });
});