Receiving Error in Chrome Extension: Unchecked runtime.lastError: Could not establish connection. Receiving end does not exist - google-chrome

Question

I'm trying to create a very simple Chrome extension that will allow me to highlight a word on a webpage, right click to open the context menu, and then search it on a database called Whitaker's Words by simply appending the word to the search URL. I'm continuing to receive
"Unchecked runtime.lastError: Could not establish connection. Receiving end does not exist."
as an error every time I run the code and attempt to use the context menu.
At the moment, I have already taken the steps to disable all other extensions and I attempted to use the port documentation on the Chrome Messaging Docs but I wasn't able to resolve the issue that way.
background.js
chrome.contextMenus.create({
title: "Search Whitaker's Words",
contexts: ["selection"]
});
chrome.contextMenus.onClicked.addListener(function() {
chrome.runtime.sendMessage({ method: "getSelection" }, function (response) {
sendToWW(response.data);
});
});
function sendToWW(selectedText) {
var serviceCall = 'http://archives.nd.edu/cgi-bin/wordz.pl?keyword=' + selectedText;
chrome.tabs.create({ url: serviceCall });
}
Here, I create a context menu and when the menu item is clicked, I send a message to the context script asking for the highlighted selection. I then return this to another function in background.js that will create a new tab with the search query.
content.js
chrome.runtime.onMessage.addListener(function (message) {
if (message.method === "getSelection"){
var word = window.getSelection().toString().trim();
console.log(word);
chrome.runtime.sendMessage({ data: word });
}
else
chrome.runtime.sendMessage({}); // snub them.
});
I listen here for the message and then take a selection from the window, trim, and send it back.
manifest.json
{
"manifest_version": 2,
"name": "Latinate",
"version": "0.1",
"description": "Aid in Latin translation using Whitaker's Words",
"content_scripts": [
{
"matches": [
"<all_urls>"
],
"js": [
"jquery-3.4.1.min.js",
"content.js"
]
}
],
"background": {
"scripts": [
"background.js"
]
},
"permissions": [
"contextMenus",
"tabs"
],
"browser_action": {
"default_icon": "icon.png",
"default_popup": "popup.html"
}
}
Any and all help would be appreciated! I've tried nearly everything I could find that seemed to apply.

Answer 1

The error message says there is no message listener on the other side. And indeed there is none because a message listener is a function registered with chrome.runtime.onMessage.addListener - in your extension only the content script has such a listener.
Instead of sending a new message back, send the response using sendResponse function which is passed as a parameter to the onMessage listener
(see also the messaging tutorial).
Another problem is that to send a message to a tab you need to use a different method: chrome.tabs.sendMessage with a tab id as the first parameter.
background script:
chrome.contextMenus.onClicked.addListener((info, tab) => {
chrome.tabs.sendMessage(tab.id, {method: 'getSelection'}, response => {
sendToWW(response.data);
});
});
content script:
chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
if (message.method === 'getSelection') {
var word = window.getSelection().toString().trim();
console.log(word);
sendResponse({ data: word });
} else {
sendResponse({});
}
});