Simple: exercise20 test passed

lib/index.js

@@ -1,16 +1,59 @@
 !function (root, doc) {
 
   class Delegator {
-    constructor (selector/* root选择器 */) {
+    constructor(selector/* root选择器 */) {
       // TODO
+      this.root = doc.querySelector(selector);
+      /**
+       * 每一种事件类型定义一个委托，并以事件类型命名，比如click
+       * delegators={
+       *   'click':{
+       *             delegator:delegatorFun,
+       *             listeners:[]
+       *           }
+       * }
+       */
+      this.delegators = {};
     }
 
-    on (event/* 绑定事件 */, selector/* 触发事件节点对应选择器 */, fn/* 出发函数 */) {
+    createDelegator(eventName) {
+      return (e) => {
+        let event = e || window.event;
+        for (let i = 0, len = event.path.length; i < len; i++) {
+          let target = event.path[i];
+          this.delegators[eventName].listeners.forEach((item) => {
+            if (target.matches(item.selector)) {
+              item.fn.call(target, event);
+            }
+          });
+          if (target === this.root) return;
+        }
+      };
+    }
+
+    on(event/* 绑定事件 */, selector/* 触发事件节点对应选择器 */, fn/* 出发函数 */) {
       // TODO
+      if (!this.delegators[event]) {
+        let delegator = this.createDelegator(event);
+        this.delegators[event] = {
+          delegator: delegator,
+          listeners: []
+        };
+        // console.log(this.delegators[event].delegator);
+        this.root.addEventListener(event, this.delegators[event].delegator);
+      }
+      this.delegators[event].listeners.push({
+        selector,
+        fn
+      });
+      return this;
     }
 
-    destroy () {
+    destroy() {
       // TODO
+      Object.keys(this.delegators).forEach(event => {
+        this.root.removeEventListener(event, this.delegators[event].delegator);
+      });
     }
   }
 

lib/polyfill.js

@@ -0,0 +1,14 @@
+if (!Element.prototype.matches) {
+  Element.prototype.matches =
+    Element.prototype.matchesSelector ||
+    Element.prototype.mozMatchesSelector ||
+    Element.prototype.msMatchesSelector ||
+    Element.prototype.oMatchesSelector ||
+    Element.prototype.webkitMatchesSelector ||
+    function (s) {
+      var matches = (this.document || this.ownerDocument).querySelectorAll(s),
+        i = matches.length;
+      while (--i >= 0 && matches.item(i) !== this) { }
+      return i > -1;
+    };
+}