diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..508cf54
--- /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": "https://registry.npmjs.org/should/-/should-11.2.1.tgz",
+      "integrity": "sha1-kPVRRVUtAc/CAGZuToGKHJZw7aI=",
+      "dev": true,
+      "requires": {
+        "should-equal": "1.0.1",
+        "should-format": "3.0.3",
+        "should-type": "1.4.0",
+        "should-type-adaptors": "1.1.0",
+        "should-util": "1.0.0"
+      }
+    },
+    "should-equal": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/should-equal/-/should-equal-1.0.1.tgz",
+      "integrity": "sha1-C26VFvJgGp+wuy3MNpr6HH4gCvc=",
+      "dev": true,
+      "requires": {
+        "should-type": "1.4.0"
+      }
+    },
+    "should-format": {
+      "version": "3.0.3",
+      "resolved": "https://registry.npmjs.org/should-format/-/should-format-3.0.3.tgz",
+      "integrity": "sha1-m/yPdPo5IFxT04w01xcwPidxJPE=",
+      "dev": true,
+      "requires": {
+        "should-type": "1.4.0",
+        "should-type-adaptors": "1.1.0"
+      }
+    },
+    "should-type": {
+      "version": "1.4.0",
+      "resolved": "https://registry.npmjs.org/should-type/-/should-type-1.4.0.tgz",
+      "integrity": "sha1-B1bYzoRt/QmEOmlHcZ36DUz/XPM=",
+      "dev": true
+    },
+    "should-type-adaptors": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/should-type-adaptors/-/should-type-adaptors-1.1.0.tgz",
+      "integrity": "sha512-JA4hdoLnN+kebEp2Vs8eBe9g7uy0zbRo+RMcU0EsNy+R+k049Ki+N5tT5Jagst2g7EAja+euFuoXFCa8vIklfA==",
+      "dev": true,
+      "requires": {
+        "should-type": "1.4.0",
+        "should-util": "1.0.0"
+      }
+    },
+    "should-util": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/should-util/-/should-util-1.0.0.tgz",
+      "integrity": "sha1-yYzaN0qmsZDfi6h8mInCtNtiAGM=",
+      "dev": true
+    }
+  }
+}
diff --git a/test/test.js b/test/test.js
index 63a72e4..bf5beb3 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1,49 +1,57 @@
+// 测试套件
 describe('this', function () {
-  it('setTimeout', function (done) {
-    var obj = {
-      say: function () {
-        setTimeout(() => {
-          // this 是什么？想想为什么？
-          this.should.equal(null)
-          done()
-        }, 0)
-      }
-    }
-    obj.say()
-  }) 
-
-  it('global', function () {
-    function test() {
-      // this 是什么？想想为什么？
-      this.should.equal(null)
-    }
-    test()
-  })
+    it('setTimeout', function (done) {
+        var obj = {
+            say: function () {
+                setTimeout(() => {
+                    // this 是什么？想想为什么？
+                    // this.should.equal(null)
+                    this.should.equal(obj)
+                    done()
+                }, 0)
+            }
+        }
+        obj.say()
+    })
 
-  describe('bind', function () {
-    it('bind undefined', function () {
-      var obj = {
-        say: function () {
-          function _say() {
+    it('global', function () {
+        function test() {
             // this 是什么？想想为什么？
-            this.should.equal(null)
-          }
-          return _say.bind(obj)
-        }()
-      }
-      obj.say()
+            // this.should.equal(null)
+            // 非严格模式下, 在node 中 this指向 global 全局对象
+            // console.log(global);
+            this.should.equal(global)
+        }
+
+        test()
     })
 
-    it('bind normal', function () {
-      var obj = {}
-      obj.say = function () {
-        function _say() {
-          // this 是什么？想想为什么？
-          this.should.equal(null)
-        }
-        return _say.bind(obj)
-      }()
-      obj.say()
+    describe('bind', function () {
+        it('bind undefined', function () {
+            var obj = {
+                say: function () {
+                    function _say() {
+                        // this 是什么？想想为什么？
+                        this.should.equal(global)
+                    }
+                    // 函数立即执行
+                    return _say.bind(obj)
+                }()
+            }
+            obj.say()
+        })
+
+        it('bind normal', function () {
+            var obj = {}
+            obj.say = function () {
+                function _say() {
+                    // this 是什么？想想为什么？
+                    this.should.equal(obj)
+                }
+
+                return _say.bind(obj)
+            }()
+            obj.say()
+        })
     })
-  })
-})
\ No newline at end of file
+})