var test = {
  _age: 18,
  get age() {
   console.log('触发get');
   //直接会this.age会进入死递归的
   return this._age;
  },
  set age(age) {
   console.log('触发set');
   this._age = age;
  }
 };

var _age = 18;
 var test = {
  get age() {
   console.log('触发get');
   //直接会this.age会进入死递归的
   return _age;
  },
  set age(age) {
   console.log('触发set');
   _age = age;
  }
 };

function test() {
  var _age = 18;
  Object.defineProperty(this, "age", {
   get: function () {
    console.log('触发get');
    return _age;
   },
   set: function (value) {
    console.log('触发set')
    _age = value;
   }
  });
 }
 var t = new test();
 t.age=18;

<div id="test">
 <p>name:</p>
 <p>age:</p>
</div>

function Element(id, initData) {
 var self = this;
 var el = document.getElementById(id);
 var templet = el.innerHTML;
 var _data = null;

 if (initData) {
 _data = {};
 for (var variable in initData) {
  _data[variable] = initData[variable];
  bind(variable, self);
 }
 }

 function bind(variable, obj) {
 Object.defineProperty(self, variable, {
  set: function (value) {
  //使用_data里的数据，避免死递归
  _data[variable] = value;
  //每次被设置新值的时候重新渲染界面
  render();
  },
  get: function () {
  return _data[variable];
  },
 });
 }

 //渲染
 function render() {
 var temp = templet;
 temp = temp.replace(/\{\{(.*)\}\}/g, function (s, t) {
  if (_data[t]) {
  return _data[t];
  }
 });
 el.innerHTML = temp;
 }

 //初始化时候手动渲染一次
 render();
}

var app = new Element('test', {
 name: 'zhangsan',
 age: 18
})

<div id="test">
 <input type="text" value="">
 <br>
 <span></span>
</div>

function Element(id, initData) {
 var self = this;
 var el = document.getElementById(id);
 var templet = el.innerHTML;
 var input = el.getElementsByTagName('input')[0];
 var _data = initData;

 Object.defineProperty(self, 'data', {
 set: function (value) {
  _data = value;
  render();
 },
 get: function () {
  return _data;
 },
 });

 //渲染
 function render() {
 var temp = templet;
 temp = temp.replace(/\{\{(data)\}\}/g, function (s, t) {
  return _data;
 });
 el.innerHTML = temp;

 //重新添加事件，其实应该用事件委托的
 input = el.getElementsByTagName('input')[0];
 inputchange();
 input.focus();
 }

 function inputchange() {
 if (window.attachEvent) {
  input.attachEvent("oninput", temp);
 } else if (window.addEventListener) {
  input.addEventListener("input", temp, false);
 }

 function temp() {
  self.data = input.value;
 }
 }

 //初始化时候手动渲染一次
 render();
}
var app = new Element('test', '');