diff --git a/2019/Aug/Week4/reactive-variables.js b/2019/Aug/Week4/reactive-variables.js
index 15981f3..e9e07f1 100644
--- a/2019/Aug/Week4/reactive-variables.js
+++ b/2019/Aug/Week4/reactive-variables.js
@@ -1,8 +1,64 @@
+function observer(obj, target) {
+  const indeps = {};
+  const valueCache = {};
+  const waitUpdate = {};
+  let currentGetter = '';
+
+  // eslint-disable-next-line guard-for-in,no-restricted-syntax
+  for (const key in obj) {
+    if (!Object.prototype.hasOwnProperty.call(obj, key)) {
+      break;
+    }
+
+    let value = obj[key];
+
+    Object.defineProperty(target, key, {
+      // eslint-disable-next-line no-loop-func
+      get() {
+        if (currentGetter !== '') {
+          // 获取依赖
+          if (!indeps[key]) {
+            indeps[key] = {};
+          }
+
+          indeps[key][currentGetter] = true;
+        }
+
+        if (typeof value === 'function') {
+          currentGetter = key;
+
+          if (valueCache[key] && !waitUpdate[key]) {
+            return valueCache[key];
+          }
+
+          const getterValue = value.call(target);
+          currentGetter = '';
+          valueCache[key] = getterValue;
+
+
+          delete waitUpdate[key];
+          return getterValue
+        }
+        return value;
+      },
+      set(v) {
+        value = v;
+
+        // 如果该key被依赖了
+        if (indeps[key]) {
+          // 将依赖key的方法名放入待更新对象
+          Object.assign(waitUpdate, indeps[key]);
+        }
+      },
+      enumerable: true,
+    })
+  }
+}
 /**
  * 响应式变量
  */
 module.exports = class ReactiveVariables {
   constructor(variables) {
-
+    observer(variables, this)
   }
 }