chrome.runtime.sendmessage not working code example

Example 1: chrome.runtime.sendmessage

chrome.runtime.sendMessage({greeting: "hello"}, function(response) {  console.log(response.farewell);});

Example 2: chrome.runtime.sendmessage

chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {  chrome.tabs.sendMessage(tabs[0].id, {greeting: "hello"}, function(response) {    console.log(response.farewell);  });});