如何将文本字段值传递给Javascript中的变量

Question

i have the below script where i want to pass the text field value to a variable and display in alert window

    <form name='searchdata' id="search_form" >
    <div class="col-xs-4" id="form_submit_ins">
    <label for="usr">Search Instance</label>
    <input type="text" class="form-control" id="ins" id"searchval" placeholder="Instance Name"><br/>
    <button class="btn btn-danger navbar-btn" onclick="form_submit();" >Search</button>
    </div>
    <div>

    </div>
    </form>
    </div>
     <script type="text/javascript">
      function form_submit() {
      var item = document.getElementById('searchval').value;
        alert(item);

    }

Answer 1

You have a typo:

id"searchval"

Should be:

id="searchval"

Answer 2

id应等于searchval，即id="searchval"

Answer 3

There is something wrong with your HTML (does it have two ID fields? Is one missing a "=" sign?

Your code should work if you fix the HTML to:

<input type="text" class="form-control" id="searchval" placeholder="Instance Name">

Answer 4

Your input has two id 's, it can only have one id

change:

<input type="text" class="form-control" id="ins" id"searchval" placeholder="Instance Name">

To:

<input type="text" class="form-control" id="searchval" placeholder="Instance Name">