现代浏览器实现了Notification API。下面是一个示例：

(function() {
  var button, output;

  function scheduleNotifyTheUser() {
    output.innerHTML = "Stand by…";
    setTimeout(notifyTheUser, 1000);
  }
  
  function notifyTheUser() {
    output.innerHTML = "Ding! You have a message!";
    new Notification("Something Happened", {
      body: "You should totally check this out!"
    });
  }
  
  document.addEventListener("DOMContentLoaded", function() {
    button = document.getElementById("gobtn");
    output = document.getElementById("output");
    output.innerHTML = "Requesting permission…";
    Notification.requestPermission(function(permission) {
      if (permission !== "granted") {
        output.innerHTML = "Notifications disabled.";
        return;
      }
      button.addEventListener("click", scheduleNotifyTheUser);
      output.innerHTML = "Ready.";
    });
  });
})();

<button id="gobtn">Make something happen in one second from now</button>
<div id="output"></div>