diff --git a/lib/index.js b/lib/index.js
index 8d2deb0..44dca7d 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -3,16 +3,43 @@
   class Delegator {
     constructor (selector/* root选择器 */) {
       // TODO
+      this.root = doc.querySelector(selector);
+      this.eventCollection = {};
+      // Using `bind this` not `arrow function` for prevent creating multiple functions
+      // Also prevent trigger multiple click
+      this.handleEvent = this.handleEvent.bind(this);
     }
 
-    on (event/* 绑定事件 */, selector/* 触发事件节点对应选择器 */, fn/* 出发函数 */) {
+    handleEvent(e) {
+      const eventPath = e.path;
+      const type = this.eventCollection[e.type];
+      if (!type) return;
+      for (let i = 0; i < eventPath.length; i++) {
+        if (eventPath[i] === e.currentTarget) return;
+        type[eventPath[i]] && type[eventPath[i]].call(eventPath[i], e);
+      }
+    }
+
+    on (event/* 绑定事件 */, selector/* 触发事件节点对应选择器 */, fn/* 触发函数 */) {
       // TODO
+      if (!this.eventCollection[event]) {
+        this.eventCollection[event] = {};
+      }
+
+      // It may not be a good way, saved a big element as key and used querySelector.
+      Object.assign(this.eventCollection[event], { [doc.querySelector(selector)]: fn });
+      this.root.addEventListener(event, this.handleEvent);
+      return this;
     }
 
     destroy () {
       // TODO
+      Object.keys(this.eventCollection).forEach(event => {
+        this.root.removeEventListener(event, this.handleEvent);
+      })
+      this.eventCollection = {};
     }
   }
 
   root.Delegator = Delegator
-}(window, document)
\ No newline at end of file
+}(window, document)