v-model （v2 原理）-526互联

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <input type="text" placeholder="请输入名称" id="username">
  显示值：<p id="uName"></p>
 
  <script>
    let obj = {}
    Object.defineProperty(obj,'username',{
      get: function(a){
        console.log(a,"取之")
      },
      set: function(b){
        console.log(b,"shezhi")
        document.getElementById('uName').innerText = b;
      }
    })

    document.getElementById("username").addEventListener('keyup',function(){
      obj.username = event.target.value
    })
  </script>
</body>
</html>