js控制input的value时提示value未定义

Question

    <input type='text' value='用户名' />

    <input type='text' value='用户名' />

    <script type="text/javascript">

        function values(){

            var get_input = document.getElementsByTagName("input");

            for (var i=0;i<get_input.length;i++)

            {    

                get_input[i].addEventListener('focus',function(){if(value==defaultValue){value='';}});

            }

        };

        values();

    </script>

上述代码为什么提示这一行：get_input[i].addEventListener('focus',function(){if(value==defaultValue){value='';}})中的value未定义？如何解决呢？谢谢

Answer 1

你这里的value呢，是谁的value呢？function values() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var get_input = document.getElementsByTagName("input");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; for(var i = 0; i < get_input.length; i++) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; get_input[i].addEventListener('focus', function() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if(this.value == this.defaultValue) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; this.value = '';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; });&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; };&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; values();