Message: add ability to close all Messages #3941 (#3966)

examples/docs/en-US/message.md

@@ -191,6 +191,7 @@ import { Message } from 'element-ui';
 ```
 
 In this case you should call `Message(options)`. We have also registered methods for different types, e.g. `Message.success(options)`.
+You can call `Message.closeAll()` to manually close all the instances.
 
 ### Options
 | Attribute      | Description          | Type      | Accepted Values       | Default  |

examples/docs/zh-CN/message.md

@@ -191,6 +191,7 @@ import { Message } from 'element-ui';
 ```
 
 此时调用方法为 `Message(options)`。我们也为每个 type 定义了各自的方法，如 `Message.success(options)`。
+并且可以调用 `Message.closeAll()` 手动关闭所有实例。
 
 ### Options
 | 参数      | 说明          | 类型      | 可选值                           | 默认值  |

packages/message/src/main.js

@@ -58,4 +58,10 @@ Message.close = function(id, userOnClose) {
   }
 };
 
+Message.closeAll = function() {
+  for (let i = instances.length - 1; i >= 0; i--) {
+    instances[i].close();
+  }
+};
+
 export default Message;

test/unit/specs/message.spec.js

@@ -41,6 +41,24 @@ describe('Message', () => {
     }, 500);
   });
 
+  it('close all', done => {
+    Message({
+      message: '夏天',
+      duration: 0
+    });
+    Message({
+      message: '淑女',
+      duration: 0
+    });
+    setTimeout(() => {
+      Message.closeAll();
+      setTimeout(() => {
+        expect(document.querySelector('.el-message')).to.not.exist;
+        done();
+      }, 500);
+    }, 500);
+  });
+
   it('create', () => {
     Message('娜梅莉亚');
     expect(document.querySelector('.el-message')).to.exist;