es6.js

function setChildTextNode(elementId, text) {
    document.getElementById(elementId).innerText = text;
}
// Tests the roundtrip time of sendRequest().
function testRequest() {
    setChildTextNode("resultsRequest", "running...");
    chrome.tabs.query({active: true, currentWindow: true}, tabs => {
        const start = new Date().getTime();
        chrome.tabs.sendMessage(tabs[0].id, {counter: 1}, function handler(response) {
            console.log(response);
            const counter = response.counter;
            if (counter < 1000) {
                chrome.tabs.sendMessage(tabs[0].id, {counter}, handler);
            } else {
                const end = new Date().getTime();
                const timer = end - start;
                const sec = Math.round(timer / counter);
                setChildTextNode("resultsRequest", `${sec} sec`);
            }
        });
    });
}
// Tests the roundtrip time of Port.postMessage() after opening a channel.
function testConnect() {
    setChildTextNode("resultsConnect", "running...");
    chrome.tabs.query({active: true, currentWindow: true}, tabs => {
        const start = new Date().getTime();
        const port = chrome.tabs.connect(tabs[0].id);
        port.postMessage({counter: 1});
        port.onMessage.addListener(response => {
            console.log(response);
            const counter = response.counter;
            if (counter < 1000) {
                port.postMessage({counter});
            } else {
                const end = new Date().getTime();
                const timer = end - start;
                const usec = Math.round(timer / counter);
                setChildTextNode("resultsConnect", `${usec} usec`);
            }
        });
    });
}
document.addEventListener('DOMContentLoaded', () => {
    document.querySelector('#testRequest').addEventListener(
        'click', testRequest);
    document.querySelector('#testConnect').addEventListener(
        'click', testConnect);
});