JavaScript 中 getter 和 setter 原理及 Object.defineProperty 应用

function Archiver() {
 var temperature = null;
 var archive = [];

 Object.defineProperty(this, 'temperature', {
  get: function() {
   console.log('get!');
   return temperature;
  },
  set: function(value) {
   temperature = value;
   archive.push({ val: temperature });
  }
 });

 this.getArchive = function() { return archive; };
}

var arc = new Archiver();
arc.temperature; // 'get!'
arc.temperature = 11;
arc.temperature = 13;
arc.getArchive(); // [{ val: 11 }, { val: 13 }]

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <h1 id="testTime" z:bind="time">0s</h1>
<script>

  // 双向绑定
  function bind_data(ele, arg){
    var bindAttributeName = 'z:bind';
    var data = JSON.parse(JSON.stringify(arg)) || {};
    Object.keys(arg).forEach(function(argKey, index, array){
      Object.defineProperty(arg, argKey, {
        get: function(){
          return data[argKey];
        },
        set: function(value){
          if(ele.getAttribute(bindAttributeName) !== argKey) {
            return;
          }
          if(ele.tagName === 'INPUT'){
            ele.value = value;
          }else{
            ele.innerHTML = value;
          }
          data[argKey] = value;
        }
      });
      arg[argKey] = arg[argKey];
    });
    var key = ele.getAttribute(bindAttributeName);
    if((ele.tagName === 'INPUT' || ele.tagName === 'TEXTAREA') && arg[key]){
      ele.addEventListener('input', function(e){
        data[key] = ele.value;
      });
    }
  }


  /*
  例子很简单，直接改变对象属性，就直接
  反馈到了DOM上，就好像是一个钩子，改变
  这个对象的属性，这个属性的钩子把它绑
  定的DOM的数据进行修改
   */ 
  var start = (new Date()).getTime();
  var now;
  var b = {time: '0s'};
  bind_data(document.getElementById('testTime'), b);
  setInterval(function(){
    var now = (new Date()).getTime();
    b.time = ((now - start)/1000) + 's'
  }, 1);

</script>
</body>
</html>