Question

I found this example in a JavaScript book

// Checks to see if the DOM is ready for navigation
function isDOMReady() {
    // If we already figured out that the page is ready, ignore

    if (domReady.done) return false;
    // Check to see if a number of functions and elements are
    // able to be accessed
    if (document && document.getElementsByTagName && document.getElementById && document.body) {
        // If they're ready, we can stop checking
        clearInterval(domReady.timer);
        domReady.timer = null;
        // Execute all the functions that were waiting
        for (var i = 0; i < domReady.ready.length; i++)
        domReady.ready[i]();
        // Remember that we're now done
        domReady.ready = null;
        domReady.done = true;
    }
}

// calling the domReady function
domReady(function () {
    alert("The DOM is loaded!");
    tag("h1")[0].style.border = "4px solid black";
});

Want to understand that what domReady.done, domReady.timer means?

Answer 1

domReady.done is a flag that will be set to true as soon as the DOM is ready. domReady.timer is the reference / handle to an interval started with window.setInterval so that it can be cleared with window.clearInterval() as soon as the DOM is ready because there is no need to check any longer.