!51 update docs/component/radio.md.

* update docs/component/radio.md.

docs/component/radio.md

@@ -85,7 +85,7 @@ export default {
     methods: {
         radioChange: function(evt) {
             for (let i = 0; i < this.items.length; i++) {
-                if (this.items[i].value === evt.target.value) {
+                if (this.items[i].value === evt.detail.value) {
                     this.current = i;
                     break;
                 }