diff --git a/.gitignore b/.gitignore
index b512c09..eb79dd5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-node_modules
\ No newline at end of file
+node_modules
+.idea
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..4742ba2
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,62 @@
+{
+  "name": "exercise4",
+  "version": "0.0.1",
+  "lockfileVersion": 1,
+  "requires": true,
+  "dependencies": {
+    "should": {
+      "version": "11.2.1",
+      "resolved": "http://registry.npm.taobao.org/should/download/should-11.2.1.tgz",
+      "integrity": "sha1-kPVRRVUtAc/CAGZuToGKHJZw7aI=",
+      "dev": true,
+      "requires": {
+        "should-equal": "^1.0.0",
+        "should-format": "^3.0.2",
+        "should-type": "^1.4.0",
+        "should-type-adaptors": "^1.0.1",
+        "should-util": "^1.0.0"
+      }
+    },
+    "should-equal": {
+      "version": "1.0.1",
+      "resolved": "http://registry.npm.taobao.org/should-equal/download/should-equal-1.0.1.tgz",
+      "integrity": "sha1-C26VFvJgGp+wuy3MNpr6HH4gCvc=",
+      "dev": true,
+      "requires": {
+        "should-type": "^1.0.0"
+      }
+    },
+    "should-format": {
+      "version": "3.0.3",
+      "resolved": "http://registry.npm.taobao.org/should-format/download/should-format-3.0.3.tgz",
+      "integrity": "sha1-m/yPdPo5IFxT04w01xcwPidxJPE=",
+      "dev": true,
+      "requires": {
+        "should-type": "^1.3.0",
+        "should-type-adaptors": "^1.0.1"
+      }
+    },
+    "should-type": {
+      "version": "1.4.0",
+      "resolved": "http://registry.npm.taobao.org/should-type/download/should-type-1.4.0.tgz",
+      "integrity": "sha1-B1bYzoRt/QmEOmlHcZ36DUz/XPM=",
+      "dev": true
+    },
+    "should-type-adaptors": {
+      "version": "1.1.0",
+      "resolved": "http://registry.npm.taobao.org/should-type-adaptors/download/should-type-adaptors-1.1.0.tgz",
+      "integrity": "sha1-QB5/M7VTMDOUTVzYvytlAneS4no=",
+      "dev": true,
+      "requires": {
+        "should-type": "^1.3.0",
+        "should-util": "^1.0.0"
+      }
+    },
+    "should-util": {
+      "version": "1.0.0",
+      "resolved": "http://registry.npm.taobao.org/should-util/download/should-util-1.0.0.tgz",
+      "integrity": "sha1-yYzaN0qmsZDfi6h8mInCtNtiAGM=",
+      "dev": true
+    }
+  }
+}
diff --git a/test/test.js b/test/test.js
index 63a72e4..41d4dd8 100644
--- a/test/test.js
+++ b/test/test.js
@@ -3,19 +3,19 @@ describe('this', function () {
     var obj = {
       say: function () {
         setTimeout(() => {
-          // this 是什么？想想为什么？
-          this.should.equal(null)
+          // 箭头函数跟函数的调用位置无关，this的指向是最靠近的父函数的作用域，即是say函数的调用对象
+          this.should.equal(obj);
           done()
         }, 0)
       }
     }
     obj.say()
-  }) 
+  })
 
   it('global', function () {
     function test() {
-      // this 是什么？想想为什么？
-      this.should.equal(null)
+      // 全局调用
+      this.should.equal(global)
     }
     test()
   })
@@ -25,8 +25,9 @@ describe('this', function () {
       var obj = {
         say: function () {
           function _say() {
-            // this 是什么？想想为什么？
-            this.should.equal(null)
+            // 在定义函数的时候立即执行函数，虽然使用bind绑定obj对象，但是此时obj还未创建完毕，undefined
+              // bind在绑定的对象为undefined的时候，默认是绑定全局对象，此时执行的为node环境，所以为global
+            this.should.equal(global)
           }
           return _say.bind(obj)
         }()
@@ -39,11 +40,11 @@ describe('this', function () {
       obj.say = function () {
         function _say() {
           // this 是什么？想想为什么？
-          this.should.equal(null)
+          this.should.equal(obj)
         }
         return _say.bind(obj)
       }()
       obj.say()
     })
   })
-})
\ No newline at end of file
+})