⼯⼚模式

      提供创建对象的接⼝，把成员对象的创建⼯作转交给⼀个外部对象，好处在于消除对象之间的耦合(也就

是相互影响)

      常⻅的例⼦，我们的弹窗，message，对外提供的api，都是调⽤api，然后新建⼀个弹窗或者Message

的实例，就是典型的⼯⼚模式

     

const Notification = function(options) {

if (Vue.prototype.$isServer) return;

options = options || {};

const userOnClose = options.onClose;

const id = 'notification_' + seed++;

const position = options.position || 'top-right';

options.onClose = function() {

Notification.close(id, userOnClose);

};

instance = new NotificationConstructor({

data: options

});

if (isVNode(options.message)) {

instance.$slots.default = [options.message];

options.message = 'REPLACED_BY_VNODE';

}

instance.id = id;

instance.$mount();

document.body.appendChild(instance.$el);

instance.visible = true;

instance.dom = instance.$el;

instance.dom.style.zIndex = PopupManager.nextZIndex();

let verticalOffset = options.offset || 0;

instances.filter(item => item.position === position).forEach(item => {

verticalOffset += item.$el.offsetHeight + 16;

});

verticalOffset += 16;

instance.verticalOffset = verticalOffset;

instances.push(instance);

return instance;

};