SOURCE

$(document).ready(function() {
  // 定义sk变量，用逗号分隔
  var sk = "";

  // 监听下拉菜单的变化
  $('#mySelect').change(function() {
    var selectedOption = $(this).find('option:selected');
    var selectedSk = selectedOption.attr('sk');
    $('#result').text(selectedSk);
  });
});

<select id="mySelect">
  <option sk='123' value="1">ykm</option>
  <option sk='577' value="2">tko</option>
  <option sk='890' value="3">test</option>
</select>
<div id="result"></div>