事件代理完成

lib/index.js

@@ -3,14 +3,43 @@
   class Delegator {
     constructor (selector/* root选择器 */) {
       // TODO
+      this.root = document.querySelector(selector);
+      this.eventMap = {};
+      // 所有的事件都绑定到this.root上，同一个事件只绑定一次
+      this.delegator = (e) => {
+        const delegatorTarget = e.currentTarget;
+        let currentTarget = e.target;
+        const type = e.type;
+        const eventQueue = this.eventMap[type];
+        while (currentTarget !== delegatorTarget) {
+          eventQueue.forEach((target) => {
+            if (currentTarget.matches(target.selector)) {
+              target.fn.call(currentTarget, e);
+            }
+          });
+          currentTarget = currentTarget.parentNode;
+        }
+      };
     }
 
     on (event/* 绑定事件 */, selector/* 触发事件节点对应选择器 */, fn/* 出发函数 */) {
-      // TODO
+      // TODO 
+      if (!this.eventMap[event]) {
+        this.eventMap[event] = [];
+        this.root.addEventListener(event, this.delegator, false);
+      }
+      this.eventMap[event].push({
+        selector,
+        fn
+      });
+      return this;
     }
 
     destroy () {
       // TODO
+      for (let [type,] of Object.entries(this.eventMap)) {
+        this.root.removeEventListener(type, this.delegator, false);
+      }
     }
   }