diff --git a/2019/Aug/Week4/reactive-variables.js b/2019/Aug/Week4/reactive-variables.js
index 15981f3..80f6901 100644
--- a/2019/Aug/Week4/reactive-variables.js
+++ b/2019/Aug/Week4/reactive-variables.js
@@ -1,8 +1,75 @@
 /**
  * 响应式变量
  */
-module.exports = class ReactiveVariables {
-  constructor(variables) {
+class Dep {
+  constructor () {
+    this.deps = [];
+  }
+
+  depend () {
+    if (Dep.target && this.deps.indexOf(Dep.target) === -1) {
+      this.deps.push(Dep.target);
+    }
+  }
 
+  notify () {
+    this.deps.forEach((dep) => {
+      dep();
+    })
   }
 }
+
+class Observable {
+  constructor (obj) {
+    Object.keys(obj).forEach((key) => {
+        Observable.defineReactive(obj, key, obj[key])
+    });
+    return obj;
+  }
+
+  static defineReactive (obj, key, val) {
+    const dep = new Dep();
+    Object.defineProperty(obj, key, {
+      get () {
+        dep.depend();
+        return val;
+      },
+      set (newVal) {
+        val = newVal;
+        dep.notify();
+      }
+    })
+  }
+}
+
+class Watcher {
+  constructor (obj, key, cb) {
+    this.cb = () => {
+      obj[key] = cb.bind(obj).call();
+    };
+    Dep.target = this.cb;
+    this.cb();
+    Dep.target = null;
+  }
+}
+
+module.exports = class ReactiveVariables {
+  constructor(variables) {
+    const attrs = {};
+    const funcs = {};
+    Object.keys(variables).forEach((key) => {
+      const variable = variables[key];
+      if(typeof variables[key] === 'function' ){
+        funcs[key] = variable;
+      }else{
+        attrs[key] = variable;
+      }
+    });
+    this.obj = new Observable(attrs);
+    Object.keys(funcs).forEach((key) => {
+      // eslint-disable-next-line
+      new Watcher(this.obj, key, funcs[key]);
+    });
+    return this.obj;
+  }
+};
\ No newline at end of file