Various vanilla js replacements for jQuery methods

utilities.js

module.exports = {

extend: function extend() {
        for (var i = 1; i < arguments.length; i++)
            for(var key in arguments[i])
                if(arguments[i].hasOwnProperty(key))
                    arguments[0][key] = arguments[i][key];
        return arguments[0];
    },

    domReady: function domReady(fn) {
        if (document.readyState !== 'loading') {
            fn();
        } else {
            document.addEventListener('DOMContentLoaded', fn);
        }
    },

    debounce: function debounce(func, wait, immediate) {
        var timeout;
        return function () {
            var context = this, args = arguments;
            var later = function () {
                timeout = null;
                if (!immediate) func.apply(context, args);
            };
            var callNow = immediate && !timeout;
            clearTimeout(timeout);
            timeout = setTimeout(later, wait);
            if (callNow) func.apply(context, args);
        };
    }
}