Стадный инстинкт :)

herd-instinct.js

var cScriptLoader = (function () {
	function cScriptLoader(files) {
		var _this = this;
		this.log = function (t) {
			console.log("ScriptLoader: " + t);
		};
		this.withNoCache = function (filename) {
			if (filename.indexOf("?") === -1)
				filename += "?no_cache=" + new Date().getTime();
			else
				filename += "&no_cache=" + new Date().getTime();
			return filename;
		};
		this.loadStyle = function (filename) {
			// HTMLLinkElement
			var link = document.createElement("link");
			link.rel = "stylesheet";
			link.type = "text/css";
			link.href = _this.withNoCache(filename);
			_this.log('Loading style ' + filename);
			link.onload = function () {
				_this.log('Loaded style "' + filename + '".');
			};
			link.onerror = function () {
				_this.log('Error loading style "' + filename + '".');
			};
			_this.m_head.appendChild(link);
		};
		this.loadScript = function (i) {
			var script = document.createElement('script');
			script.type = 'text/javascript';
			script.src = _this.withNoCache(_this.m_js_files[i]);
			var loadNextScript = function () {
				if (i + 1 < _this.m_js_files.length) {
					_this.loadScript(i + 1);
				}
			};
			script.onload = function () {
				_this.log('Loaded script "' + _this.m_js_files[i] + '".');
				loadNextScript();
			};
			script.onerror = function () {
				_this.log('Error loading script "' + _this.m_js_files[i] + '".');
				loadNextScript();
			};
			_this.log('Loading script "' + _this.m_js_files[i] + '".');
			_this.m_head.appendChild(script);
		};
		this.loadFiles = function () {
			// this.log(this.m_css_files);
			// this.log(this.m_js_files);
			for (var i = 0; i < _this.m_css_files.length; ++i)
				_this.loadStyle(_this.m_css_files[i]);
			_this.loadScript(0);
		};
		this.m_js_files = [];
		this.m_css_files = [];
		this.m_head = document.getElementsByTagName("head")[0];
		// this.m_head = document.head; // IE9+ only
		function endsWith(str, suffix) {
			if (str === null || suffix === null)
				return false;
			return str.indexOf(suffix, str.length - suffix.length) !== -1;
		}
		for (var i = 0; i < files.length; ++i) {
			if (endsWith(files[i], ".css")) {
				this.m_css_files.push(files[i]);
			} else if (endsWith(files[i], ".js")) {
				this.m_js_files.push(files[i]);
			} else
				this.log('Error unknown filetype "' + files[i] + '".');
		}
	}
	return cScriptLoader;
})();

var maleNamesArray = ['Никита', 'Константин', 'Алексей'];
var femaleNamesArray = ['Ольга', 'Илона', 'Евгения'];
var namesArray = maleNamesArray.concat(femaleNamesArray);

function getArrayRandomElement(arr) {
	if (arr && arr.length) {
		return arr[Math.floor(Math.random() * arr.length)];
	}
	// The undefined will be returned if the empty array was passed
}

function getRandomName() {
	return getArrayRandomElement(namesArray);
}

function getRandomArbitrary(min, max) {
	return Math.random() * (max - min) + min;
}

function setZIndex() {
	elements = document.getElementsByClassName("toastify");
	for (var i = 0; i < elements.length; i++) {
		elements[i].style.zIndex = "999";
	}
}

function showTooltip() {
	var randomName = getRandomName();
	Toastify({
		text: randomName + " купил(а) программу",
		duration: 3000,
		// destination: "",
		newWindow: true,
		close: true,
		gravity: "bottom", // `top` or `bottom`
		positionLeft: false, // `true` or `false`
		backgroundColor: "linear-gradient(to right, #00b09b, #96c93d)",
	}).showToast();
}


(function loop() {
	// var rand = Math.round(Math.random() * (3000 - 500)) + 500;
	var randomInt = getRandomArbitrary(3000, 6000)
	setTimeout(function () {
		showTooltip();
		setZIndex();
		loop();
	}, randomInt);
}());

var ScriptLoader = new cScriptLoader([
	"https://cdn.jsdelivr.net/npm/toastify-js/src/toastify.min.css",
	"https://cdn.jsdelivr.net/npm/toastify-js/src/toastify.min.js"
]);
ScriptLoader.loadFiles();