<div>

    <p>你好，<input id='nickName'></p>

    <div id="introduce"></div>

</div>

    <script>

        var userInfo = {};

        var a = '';

        var inp = document.getElementById('nickName');

        var odiv = document.getElementById('introduce');

        Object.defineProperty(userInfo, "nickName", {

            get: function(){

                return inp.value;

            },

            set: function(nick){

            }

        });

        Object.defineProperty(userInfo, "introduce", {

            get: function(){

            },

            set: function(introduce){

                odiv.innerHTML = introduce;

            }

        })

        inp.addEventListener("keyup",function(){

            userInfo.introduce = userInfo.nickName;

        })

    </script>