repair problem: countdown will not change when target time update (#392)

src/components/CountDown/index.js

@@ -21,9 +21,12 @@ class CountDown extends Component {
 
   componentWillReceiveProps(nextProps) {
     if (this.props.target !== nextProps.target) {
+      clearTimeout(this.timer);
       const { lastTime } = this.initTime(nextProps);
       this.setState({
         lastTime,
+      }, () => {
+        this.tick();
       });
     }
   }
@@ -76,18 +79,18 @@ class CountDown extends Component {
         clearTimeout(this.timer);
         this.setState({
           lastTime: 0,
-        });
-
+        }, () => {
           if (onEnd) {
             onEnd();
           }
+        });
       } else {
         lastTime -= this.interval;
         this.setState({
           lastTime,
-        });
-
+        }, () => {
           this.tick();
+        });
       }
     }, this.interval);
   }