Chrome扩展程序addEventListener + dispatchEvent结果添加到var

Question

我有background.js：

var responses = {}

var filter = {
  urls: ["http://*/*", "https://*/*"],
  types: ["main_frame"]
}

var options = ["responseHeaders"]

chrome.webRequest.onHeadersReceived.addListener(function(details) {
  responses[details.url] = details
}, filter, options)

chrome.runtime.onMessage.addListener(function(request, sender, sendResponse) {
  sendResponse({
    headers: responses[sender.tab.url]
  })
})

ScriptForParsing.js

var markup;
var cookies;
var headers;

$(document).ready(function() {
  parse();
});

function parse() {
  markup = document.documentElement.innerHTML;
  cookies = document.cookie;

  document.addEventListener('GetHeaders', function(event) {
    chrome.runtime.sendMessage(chrome.runtime.id, {}, {}, function(response) {
      document.dispatchEvent(new CustomEvent("GotHeaders",{
        detail: response.headers
      }))
    })
  })

}

我希望我的var标头类似于response.headers-怎么样？