Question

＆＃13;

$("#add").click(function() {
  var userValue = $('#textarea').val();
  $('#textarea').val('');
 $('#writtings').append('<p>' + userValue + '</p>');

});

$('body').on('click', '#delete', function() {
     $("#writtings p").remove();
     return false;  
  });
  
 if($('#writtings').is(':empty') ) {
  $("#delete").css("background","red");
 }else {
   $("#delete").css("background","green");
 }

＆＃13;

#writtings {
  margin-top:20px;
  width:200px;
  height:auto;
  border:1px solid #333;
}

＆＃13;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<textarea  id="textarea" placeholder="Write here!"></textarea>    
 <button id="add">Add</button>
 <button id="delete">Delete</button>
 <div id="writtings"></div>

＆＃13;

伙计们，我想检查我的div是否附加了元素。如果有附加元素，我会改变我的按钮背景。那么如何？JsFiddle

Answer 1

$("#add").click(function() {
    var userValue = $('#textarea').val();
    $('#textarea').val('');
    $('#writtings').append('<p>' + userValue + '</p>');
     if($('#writtings p')) {
        $("#delete").css("background","red");
     } 
     else {
     $("#delete").css("background","green");
     }
});

$('body').on('click', '#delete', function() {
     $("#writtings p").remove();
     $("#delete").css("background","green");
     return false;  
  });

https://jsfiddle.net/qxx50up8/1/

Answer 2

在$("#delete").css("background","green")按钮的点击事件中添加add，如下所示。

$("#add").click(function() {
    var userValue = $('#textarea').val();
    if(!userValue) retrun;

    $('#textarea').val('');
    $('#writtings').append('<p>' + userValue + '</p>');

    $("#delete").css("background","green");
});

在$("#delete").css("background", "red");按钮的点击事件中添加delete，如下所示。

$('body').on('click', '#delete', function() {
    $("#writtings p").remove();
    $("#delete").css("background", "red");

    return false;  
});

Answer 3

在您的情况下，您可以通过以下代码检查p tag是否附加到#writtings div： -

  if($('#writtings').find('p').length == 1 ) {
          $("#delete").css("background","red");
         }else {
           $("#delete").css("background","green");
    }

检查div是否有附加元素

3 个答案: