Notification.permission

Notification 的只读属性 permission 用来表明用户是否允许当前域显示Web Notification. 

var permission = Notification.permission;

permission 的类型为 DOMString . 该属性的可能值为:

• granted: 用户已经明确的授予了显示通知的权限。.
• denied: 用户已经明确的拒绝了显示通知的权限。
• default: 用户还未被询问是否授权; 这种情况下权限将视为 denied.

下面的代码片段详细的说明了，当你首次检查浏览器是否支持Notification，然后检查当前域是否被授予了发送Notification的权限，并且在发送一个通知前进行请求的用法．

function notifyMe() {
  // Let's check if the browser supports notifications
  if (!("Notification" in window)) {
    console.log("This browser does not support desktop notification");
  }

  // Let's check whether notification permissions have alredy been granted
  else if (Notification.permission === "granted") {
    // If it's okay let's create a notification
    var notification = new Notification("Hi there!");
  }

  // Otherwise, we need to ask the user for permission
  else if (Notification.permission !== 'denied' || Notification.permission === "default") {
    Notification.requestPermission(function (permission) {
      // If the user accepts, let's create a notification
      if (permission === "granted") {
        var notification = new Notification("Hi there!");
      }
    });
  }

  // At last, if the user has denied notifications, and you
  // want to be respectful there is no need to bother them any more.
}

{{Page("/en-US/docs/Web/API/Notifications_API", "Firefox OS notes")}}

{{Page("/en-US/docs/Web/API/Notifications_API", "Chrome notes")}}

{{Page("/en-US/docs/Web/API/Notifications_API", "Safari notes")}}

• Using the Notifications API
• Permissions API