Question

我正在尝试只在没有值的情况下运行if语句。

<script src="https://jqueryvalidation.org/files/lib/jquery-1.11.1.js"></script>
<script type="text/javascript">
    function checkNSC() {
        var confirmNSC = $("#SelectNsc");
        if (confirmNSC.length == 0) {
            alert("Please ensure all required fields are filled out")
        }
        else {
            alert("NSC has value")
        }

    }

</script>

HTML：

<input type="text" id="SelectNsc" />
<button onclick="checkNSC();" id="myButton">My Button</button>
</div>

我试图说明值是否为0然后显示警告说（请确保填写所有字段“。否则说”NSC有值“

谢谢，

Answer 1

应该是，

var confirmNSC = $("#SelectNsc").val();

因为$("#SelectNsc")返回一个jquery对象，所以$("#SelectNsc").length将始终返回一个大于0的值。

<script src = "https://jqueryvalidation.org/files/lib/jquery-1.11.1.js" > < /script> 
<script type = "text/javascript" >
  $(document).ready(function() {
    $("#myButton").click(function() {
      var confirmNSC = $("#SelectNsc").val().trim();
      if (confirmNSC.length == 0) {
        alert("Please ensure all required fields are filled out")
      } else {
        alert("NSC has value")
      }
    });

  })
</script>

Fiddle

Answer 2

试试这个，它工作正常

＆＃13;

<script src="https://jqueryvalidation.org/files/lib/jquery-1.11.1.js"></script>
<script type="text/javascript">
    function checkNSC() {
        var confirmNSC = $("#SelectNsc");
        if (confirmNSC.val() =='') {
            alert("Please ensure all required fields are filled out")
        }
        else {
            alert("NSC has value")
        }

    }

</script>


<input type="text" id="SelectNsc" />
<button onclick="checkNSC();" id="myButton">My Button</button>
</div>

＆＃13;

Answer 3

使用此代码：

<body>
 <script src="https://jqueryvalidation.org/files/lib/jquery-1.11.1.js"></script>
<script type="text/javascript">
    function checkNSC() {
        var confirmNSC = document.getElementById("SelectNsc").value;
        if (confirmNSC.length == 0) {
            alert("Please ensure all required fields are filled out")
        }
        else {
            alert("NSC has value")
        }

    }

</script>
    <input type="text" id="SelectNsc" />
<button onclick="checkNSC();" id="myButton">My Button</button>
</body>

或者，使用此代码：

<body>
 <script src="https://jqueryvalidation.org/files/lib/jquery-1.11.1.js"></script>
<script type="text/javascript">
    function checkNSC() {
        var confirmNSC = $("#SelectNsc").val();
        if (confirmNSC.length == 0) {
            alert("Please ensure all required fields are filled out")
        }
        else {
            alert("NSC has value")
        }

    }

</script>
    <input type="text" id="SelectNsc" />
<button onclick="checkNSC();" id="myButton">My Button</button>
</body>

如果文本框有值，为什么我不能显示警报？

3 个答案: