dom ready

domready.js

var domReady = (function() {
    var readyCallbacks = [];

    function whenReady(callback) {
        setTimeout(function() {
            callback.call(document)
        });
    }

    function completed() {
        document.removeEventListener('DOMContentLoaded', completed);
        window.removeEventListener('load', completed);
        while (readyCallbacks.length) {
            let cb = readyCallbacks.shift();
            whenReady(cb);
        }
    }

    return function(callback) {
        if (document.readyState === 'loading') {
            if (readyCallbacks.length === 0) {
                document.addEventListener('DOMContentLoaded', completed);
                window.addEventListener('load', completed);
            }
            readyCallbacks.push(callback)
        } else {
            whenReady(callback);
        }
    }
})();