根据其他选择更改动态添加的下拉菜单的选项

Question

哎呀！

堆垛机如能提供任何帮助，我们将不胜感激！好的，我有一个包含 3 个列表的下拉菜单，我需要每个列表中的 selections 来更改下一个列表的选项。我已经成功并使三个列表列表从（下拉列表 1）中的第一个 selection 自动填充，但当我 select 第一个列表中的第二个选项自动填充第三个列表时却没有。我可以使用什么语法使第三个列表选项从第一个列表中的 selection 更改？我没有包括 Flange/Groove 列表的所有选项，因为太多了。为我的菜鸟道歉

这是我的 HTML:

                 </div>
    <div class ="valvetype">
    <select class="form-control"id='firstList' name='firstList' onClick="getValveSize()">
    <option>Type</option>
    </select> 
    <select class="form-control"  id='secondList' name='secondList' onClick="getTurns()">
    <option>DN</option>
    </select>
    <select class="form-control"id='thirdList' name='thirdList' >
    <option>Turns</option>
    </select>
    <button onclick="findInArray()"class= "submit">Submit</button>

和一些 js:

         $(document).ready(function () {
    
         var list1 = document.getElementById('firstList');

         list1.options[0] = new Option('Valve Type', '');
         list1.options[1] = new Option('Thread/Solder', 'Thread/Solder');
         list1.options[2] = new Option('Flange/Groove', 'Flange/Groove');
       });
      function getValveSize(){
        var list1 = document.getElementById('firstList');
        var list2 = document.getElementById("secondList");
        var list1SelectedValue = list1.options[list1.selectedIndex].value;
    
         if (list1SelectedValue==='Thread/Solder')
         {
         
        list2.options.length=0;
        list2.options[0] = new Option('DN', '');
        list2.options[1] = new Option('10', '10');
        list2.options[2] = new Option('15', '15');
        list2.options[3] = new Option('20', '20');
        list2.options[4] = new Option('25', '25');
        list2.options[5] = new Option('32', '32');
        list2.options[6] = new Option('40', '40');
        list2.options[7] = new Option('50', '50');
        list2.options[8] = new Option('65', '65');
        
          }
         else if (list1SelectedValue==='Flange/Groove')
          {
        
        list2.options.length=0;
        list2.options[0] = new Option('DN', '');
        list2.options[1] = new Option('20', '20');
        list2.options[2] = new Option('25', '25');
        list2.options[3] = new Option('32', '32');
        list2.options[4] = new Option('40', '40');
        list2.options[5] = new Option('50', '50');
        list2.options[6] = new Option('65', '65');
        list2.options[7] = new Option('80', '80');
        list2.options[8] = new Option('100', '100');
        list2.options[9] = new Option('125', '125');
        list2.options[10] = new Option('150', '150');
        list2.options[11] = new Option('200', '200');
        list2.options[12] = new Option('250', '250');
        list2.options[13] = new Option('300', '300');
        list2.options[14] = new Option('350', '350');
        list2.options[15] = new Option('400', '400');
       }
     }  
   
    function getTurns(){
     var list1 = document.getElementById('firstList');
     var list2 = document.getElementById('secondList');
     var list3 = document.getElementById('thirdList');
     var list1SelectedValue = list1.options[list1.selectedIndex].value;
     var list2SelectedValue = list2.options[list2.selectedIndex].value;


    if ($.inArray(list2SelectedValue, ['10', '15', '20', '25']) >= 0)
    {
     
    list3.options.length=0;
    list3.options[0] = new Option('Turns', '');
    list3.options[1] = new Option('0.25', '0.25');
    list3.options[2] = new Option('0.5', '0.5');
    list3.options[3] = new Option('0.75', '0.75');
    list3.options[4] = new Option('1', '1');
    list3.options[5] = new Option('1.1', '1.1');
    list3.options[6] = new Option('1.2', '1.2');
    list3.options[7] = new Option('1.3', '1.3');
    list3.options[8] = new Option('1.4', '1.4');
    list3.options[9] = new Option('1.5', '1.5');
    list3.options[10] = new Option('1.6', '1.6');
    list3.options[11] = new Option('1.7', '1.7');
    list3.options[12] = new Option('1.8', '1.8');
    list3.options[13] = new Option('1.9', '1.9');
    list3.options[14] = new Option('2', '2');
    list3.options[15] = new Option('2.1', '2.1');
    list3.options[16] = new Option('2.2', '2.2');
    list3.options[17] = new Option('2.3', '2.3');
    list3.options[18] = new Option('2.4', '2.4');
    list3.options[19] = new Option('2.5', '2.5');
    list3.options[20] = new Option('2.6', '2.6');
    list3.options[21] = new Option('2.7', '2.7');
    list3.options[22] = new Option('2.8', '2.8');
    list3.options[23] = new Option('2.9', '2.9');
    list3.options[24] = new Option('3', '3');
    list3.options[25] = new Option('3.1', '3.1');
    list3.options[26] = new Option('3.2', '3.2');
    list3.options[27] = new Option('3.3', '3.3');
    list3.options[28] = new Option('3.4', '3.4');
    list3.options[29] = new Option('3.5', '3.5');
    list3.options[30] = new Option('3.6', '3.6');
    list3.options[31] = new Option('3.7', '3.7');
    list3.options[32] = new Option('3.8', '3.8');
    list3.options[33] = new Option('3.9', '3.9');
    list3.options[34] = new Option('4', '4');
    list3.options[35] = new Option('4.1', '4.1');
    list3.options[36] = new Option('4.2', '4.2');
    list3.options[37] = new Option('4.3', '4.3');
    list3.options[38] = new Option('4.4', '4.4');
    list3.options[39] = new Option('4.5', '4.5');
    list3.options[40] = new Option("4.6", "4.6");
    list3.options[41] = new Option("4.7", "4.7");
    list3.options[42] = new Option("4.8", "4.8");
    list3.options[43] = new Option("4.9", "4.9");
    list3.options[44] = new Option("5", "5");
    list3.options[45] = new Option("5.1", "5.1");
    list3.options[46] = new Option("5.2", "5.2");
    list3.options[47] = new Option("5.3", "5.3");
    list3.options[48] = new Option("5.4", "5.4");
    list3.options[49] = new Option("5.5", "5.5");
    list3.options[50] = new Option("5.6", "5.6");
    list3.options[51] = new Option("5.7", "5.7");
    list3.options[52] = new Option("5.8", "5.8");
    list3.options[53] = new Option("5.9", "5.9");
    list3.options[54] = new Option("6", "6");
    list3.options[55] = new Option("6.1", "6.1");
    list3.options[56] = new Option("6.2", "6.2");
    list3.options[57] = new Option("6.3", "6.3");
    list3.options[58] = new Option("6.4", "6.4");
    list3.options[59] = new Option("6.5", "6.5");
    list3.options[60] = new Option("6.6", "6.6");
    list3.options[61] = new Option("6.7", "6.7");
    list3.options[62] = new Option("6.8", "6.8");
    list3.options[63] = new Option("6.9", "6.9");
    list3.options[64] = new Option("7", "7");
    }
  
    else if ($.inArray(list2SelectedValue, ['32', '40', '50']) >= 0) {
    
    list3.options.length=0;
    list3.options[0] = new Option('Turns', '');
    list3.options[1] = new Option('0.25', '0.25');
    list3.options[2] = new Option('0.5', '0.5');
    list3.options[3] = new Option('0.75', '0.75');
    list3.options[4] = new Option('1', '1');
    list3.options[5] = new Option('1.1', '1.1');
    list3.options[6] = new Option('1.2', '1.2');
    list3.options[7] = new Option('1.3', '1.3');
    list3.options[8] = new Option('1.4', '1.4');
    list3.options[9] = new Option('1.5', '1.5');
    list3.options[10] = new Option('1.6', '1.6');
    list3.options[11] = new Option('1.7', '1.7');
    list3.options[12] = new Option('1.8', '1.8');
    list3.options[13] = new Option('1.9', '1.9');
    list3.options[14] = new Option('2', '2');
    list3.options[15] = new Option('2.1', '2.1');
    list3.options[16] = new Option('2.2', '2.2');
    list3.options[17] = new Option('2.3', '2.3');
    list3.options[18] = new Option('2.4', '2.4');
    list3.options[19] = new Option('2.5', '2.5');
    list3.options[20] = new Option('2.6', '2.6');
    list3.options[21] = new Option('2.7', '2.7');
    list3.options[22] = new Option('2.8', '2.8');
    list3.options[23] = new Option('2.9', '2.9');
    list3.options[24] = new Option('3', '3');
    list3.options[25] = new Option('3.1', '3.1');
    list3.options[26] = new Option('3.2', '3.2');
    list3.options[27] = new Option('3.3', '3.3');
    list3.options[28] = new Option('3.4', '3.4');
    list3.options[29] = new Option('3.5', '3.5');
    list3.options[30] = new Option('3.6', '3.6');
    list3.options[31] = new Option('3.7', '3.7');
    list3.options[32] = new Option('3.8', '3.8');
    list3.options[33] = new Option('3.9', '3.9');
    list3.options[34] = new Option('4', '4');
    list3.options[35] = new Option('4.1', '4.1');
    list3.options[36] = new Option('4.2', '4.2');
    list3.options[37] = new Option('4.3', '4.3');
    list3.options[38] = new Option('4.4', '4.4');
    list3.options[39] = new Option('4.5', '4.5');
    list3.options[40] = new Option('4.6', '4.6');
    list3.options[41] = new Option('4.7', '4.7');
    list3.options[42] = new Option('4.8', '4.8');
    list3.options[43] = new Option('4.9', '4.9');
    list3.options[44] = new Option('5', '5');
    list3.options[45] = new Option('5.1', '5.1');
    list3.options[46] = new Option('5.2', '5.2');
    list3.options[47] = new Option('5.3', '5.3');
    list3.options[48] = new Option('5.4', '5.4');
    list3.options[49] = new Option('5.5', '5.5');
    list3.options[50] = new Option('5.6', '5.6');
    list3.options[51] = new Option('5.7', '5.7');
    list3.options[52] = new Option('5.8', '5.8');
    list3.options[53] = new Option('5.9', '5.9');
    list3.options[54] = new Option('6', '6');
    list3.options[55] = new Option('6.1', '6.1');
    list3.options[56] = new Option('6.2', '6.2');
    list3.options[57] = new Option('6.3', '6.3');
    list3.options[58] = new Option('6.4', '6.4');
    list3.options[59] = new Option('6.5', '6.5');
    list3.options[60] = new Option('6.6', '6.6');
    list3.options[61] = new Option('6.7', '6.7');
    list3.options[62] = new Option('6.8', '6.8');
    list3.options[63] = new Option('6.9', '6.9');
    list3.options[64] = new Option('7', '7');
    list3.options[65] = new Option('7.1', '7.1');
    list3.options[66] = new Option('7.2', '7.2');
    list3.options[67] = new Option('7.3', '7.3');
    list3.options[68] = new Option('7.4', '7.4');
    list3.options[69] = new Option('7.5', '7.5');
    list3.options[70] = new Option('7.6', '7.6');
    list3.options[71] = new Option('7.7', '7.7');
    list3.options[72] = new Option('7.8', '7.8');
    list3.options[73] = new Option('7.9', '7.9');
    list3.options[74] = new Option('8', '8');
    list3.options[75] = new Option('8.1', '8.1');
    list3.options[76] = new Option('8.2', '8.2');
    list3.options[77] = new Option('8.3', '8.3');
    list3.options[78] = new Option('8.4', '8.4');
    list3.options[79] = new Option('8.5', '8.5');
    list3.options[80] = new Option('8.6', '8.6');
    list3.options[81] = new Option('8.7', '8.7');
    list3.options[82] = new Option('8.8', '8.8');
    list3.options[83] = new Option('8.9', '8.9');
    list3.options[84] = new Option('9', '9');
    list3.options[85] = new Option('9.1','9.1');
    list3.options[86] = new Option('9.2', '9.2');
    list3.options[87] = new Option('9.3', '9.3');
    list3.options[88] = new Option('9.4', '9.4');
    list3.options[89] = new Option('9.5', '9.5');
    list3.options[90] = new Option('9.6', '9.6');
    list3.options[91] = new Option('9.7', '9.7');
    list3.options[92] = new Option('9.8', '9.8');
    list3.options[93] = new Option('9.9', '9.9');
    list3.options[94] = new Option('10', '10');
     }
      else if 
     ($.inArray(list2SelectedValue, ['65']) >= 0) {
    
    list3.options.length=0;

    list3.options[0] = new Option('1', '1');
    list3.options[1] = new Option('1.1', '1.1');
    list3.options[2] = new Option('1.2', '1.2');
    list3.options[3] = new Option('1.3', '1.3');
    list3.options[4] = new Option('1.4', '1.4');
    list3.options[5] = new Option('1.5', '1.5');
    list3.options[6] = new Option('1.6', '1.6');
    list3.options[7] = new Option('1.7', '1.7');
    list3.options[8] = new Option('1.8', '1.8');
    list3.options[9] = new Option('1.9', '1.9');
    list3.options[10] = new Option('2', '2');
    list3.options[11] = new Option('2.1', '2.1');
    list3.options[12] = new Option('2.2', '2.2');
    list3.options[13] = new Option('2.3', '2.3');
    list3.options[14] = new Option('2.4', '2.4');
    list3.options[15] = new Option('2.5', '2.5');
    list3.options[16] = new Option('2.6', '2.6');
    list3.options[17] = new Option('2.7', '2.7');
    list3.options[18] = new Option('2.8', '2.8');
    list3.options[19] = new Option('2.9', '2.9');
    list3.options[20] = new Option('3', '3');
    list3.options[21] = new Option('3.1', '3.1');
    list3.options[22] = new Option('3.2', '3.2');
    list3.options[23] = new Option('3.3', '3.3');
    list3.options[24] = new Option('3.4', '3.4');
    list3.options[25] = new Option('3.5', '3.5');
    list3.options[26] = new Option('3.6', '3.6');
    list3.options[27] = new Option('3.7', '3.7');
    list3.options[28] = new Option('3.8', '3.8');
    list3.options[29] = new Option('3.9', '3.9');
    list3.options[30] = new Option('4', '4');
    list3.options[31] = new Option('4.1', '4.1');
    list3.options[32] = new Option('4.2', '4.2');
    list3.options[33] = new Option('4.3', '4.3');
    list3.options[34] = new Option('4.4', '4.4');
    list3.options[35] = new Option('4.5', '4.5');
    list3.options[36] = new Option('4.6', '4.6');
    list3.options[37] = new Option('4.7', '4.7');
    list3.options[38] = new Option('4.8', '4.8');
    list3.options[39] = new Option('4.9', '4.9');
    list3.options[40] = new Option('5', '5');
    list3.options[41] = new Option('5.1', '5.1');
    list3.options[42] = new Option('5.2', '5.2');
    list3.options[43] = new Option('5.3', '5.3');
    list3.options[44] = new Option('5.4', '5.4');
    list3.options[45] = new Option('5.5', '5.5');
    list3.options[46] = new Option('5.6', '5.6');
    list3.options[47] = new Option('5.7', '5.7');
    list3.options[48] = new Option('5.8', '5.8');
    list3.options[49] = new Option('5.9', '5.9');
    list3.options[50] = new Option('6', '6');
    list3.options[51] = new Option('6.1', '6.1');
    list3.options[52] = new Option('6.2', '6.2');
    list3.options[53] = new Option('6.3', '6.3');
    list3.options[54] = new Option('6.4', '6.4');
    list3.options[55] = new Option('6.5', '6.5');
    list3.options[56] = new Option('6.6', '6.6');
    list3.options[57] = new Option('6.7', '6.7');
    list3.options[58] = new Option('6.8', '6.8');
    list3.options[59] = new Option('6.9', '6.9');
    list3.options[60] = new Option('7', '7');
    list3.options[61] = new Option('7.1', '7.1');
    list3.options[62] = new Option('7.2', '7.2');
    list3.options[63] = new Option('7.3', '7.3');
    list3.options[64] = new Option('7.4', '7.4');
    list3.options[65] = new Option('7.5', '7.5');
    list3.options[66] = new Option('7.6', '7.6');
    list3.options[67] = new Option('7.7', '7.7');
    list3.options[68] = new Option('7.8', '7.8');
    list3.options[69] = new Option('7.9', '7.9');
    list3.options[70] = new Option('8', '8');
    list3.options[71] = new Option('8.1', '8.1');
    list3.options[72] = new Option('8.2', '8.2');
    list3.options[73] = new Option('8.3', '8.3');
    list3.options[74] = new Option('8.4', '8.4');
    list3.options[75] = new Option('8.5', '8.5');
    list3.options[76] = new Option('8.6', '8.6');
    list3.options[77] = new Option('8.7', '8.7');
    list3.options[78] = new Option('8.8', '8.8');
    list3.options[79] = new Option('8.9', '8.9');
    list3.options[80] = new Option('9', '9');
    list3.options[81] = new Option('9.1','9.1');
    list3.options[82] = new Option('9.2', '9.2');
    list3.options[83] = new Option('9.3', '9.3');
    list3.options[84] = new Option('9.4', '9.4');
    list3.options[85] = new Option('9.5', '9.5');
    list3.options[86] = new Option('9.6', '9.6');
    list3.options[87] = new Option('9.7', '9.7');
    list3.options[88] = new Option('9.8', '9.8');
    list3.options[89] = new Option('9.9', '9.9');
    list3.options[90] = new Option('10', '10');
    list3.options[91] = new Option('10.1', '10.1');
    list3.options[92] = new Option('10.2', '10.2');
    list3.options[93] = new Option('10.3', '10.3');
    list3.options[94] = new Option('10.4', '10.4');
    list3.options[95] = new Option('10.5', '10.5');
    list3.options[96] = new Option('10.6', '10.6');
    list3.options[97] = new Option('10.7', '10.7');
    list3.options[98] = new Option('10.8', '10.8');
    list3.options[99] = new Option('10.9', '10.9');
    list3.options[100] = new Option('11', '11');
    list3.options[101] = new Option('11.1', '11.1');
    list3.options[102] = new Option('11.2', '11.2');
    list3.options[103] = new Option('11.3', '11.3');
    list3.options[104] = new Option('11.4', '11.4');
    list3.options[105] = new Option('11.5', '11.5');
    list3.options[106] = new Option('11.6', '11.6');
    list3.options[107] = new Option('11.7', '11.7');
    list3.options[108] = new Option('11.8', '11.8');
    list3.options[109] = new Option('11.9', '11.9');
    list3.options[110] = new Option('12', '12');
    }


      else if 
      (list1SelectedValue.is('Flange/Groove') && list2SelectedValue.is('20', '25'))
      {

    list3.options.length=0;
    list3.options[0] = new Option('1', '1');
    list3.options[1] = new Option('1.1', '1.1');
    list3.options[2] = new Option('1.2', '1.2');
    list3.options[3] = new Option('1.3', '1.3');
    list3.options[4] = new Option('1.4', '1.4');
    list3.options[5] = new Option('1.5', '1.5');
    list3.options[6] = new Option('1.6', '1.6');
    list3.options[7] = new Option('1.7', '1.7');
    list3.options[8] = new Option('1.8', '1.8');
    list3.options[8] = new Option('1.9', '1.9');
    list3.options[9] = new Option('2', '2');
    list3.options[10] = new Option('2.1', '2.1');
    list3.options[11] = new Option('2.2', '2.2');
    list3.options[12] = new Option('2.3', '2.3');
    list3.options[13] = new Option('2.4', '2.4');
    list3.options[14] = new Option('2.5', '2.5');
    list3.options[15] = new Option('2.6', '2.6');
    list3.options[16] = new Option('2.7', '2.7');
    list3.options[17] = new Option('2.8', '2.8');
    list3.options[18] = new Option('2.9', '2.9');
    list3.options[19] = new Option('3', '3');
    list3.options[20] = new Option('3.1', '3.1');
    list3.options[21] = new Option('3.2', '3.2');
    list3.options[22] = new Option('3.3', '3.3');
    list3.options[23] = new Option('3.4', '3.4');
    list3.options[24] = new Option('3.5', '3.5');
    list3.options[25] = new Option('3.6', '3.6');
    list3.options[26] = new Option('3.7', '3.7');
    list3.options[27] = new Option('3.8', '3.8');
    list3.options[28] = new Option('3.9', '3.9');
    list3.options[29] = new Option('4', '4');
    list3.options[30] = new Option('4.1', '4.1');
    list3.options[31] = new Option('4.2', '4.2');
    list3.options[32] = new Option('4.3', '4.3');
    list3.options[33] = new Option('4.4', '4.4');
    list3.options[34] = new Option('4.5', '4.5');
    list3.options[35] = new Option('4.6', '4.6');
    list3.options[36] = new Option('4.7', '4.7');
    list3.options[37] = new Option('4.8', '4.8');
    list3.options[38] = new Option('4.9', '4.9');
    list3.options[39] = new Option('5', '5');
    list3.options[40] = new Option('5.1', '5.1');
    list3.options[41] = new Option('5.2', '5.2');
    list3.options[42] = new Option('5.3', '5.3');
    list3.options[43] = new Option('5.4', '5.4');
    list3.options[44] = new Option('5.5', '5.5');
    list3.options[45] = new Option('5.6', '5.6');
    list3.options[46] = new Option('5.7', '5.7');
    list3.options[47] = new Option('5.8', '5.8');
    list3.options[48] = new Option('5.9', '5.9');
    list3.options[49] = new Option('6', '6');
    list3.options[50] = new Option('6.1', '6.1');
    list3.options[51] = new Option('6.2', '6.2');
    list3.options[52] = new Option('6.3', '6.3');
    list3.options[53] = new Option('6.4', '6.4');
    list3.options[54] = new Option('6.5', '6.5');
    list3.options[55] = new Option('6.6', '6.6');
    list3.options[56] = new Option('6.7', '6.7');
    list3.options[57] = new Option('6.8', '6.8');
    list3.options[58] = new Option('6.9', '6.9');
    list3.options[59] = new Option('7', '7');
       }
       $('#thirdList').append(list3);
    }

Answer 1

您之前的逻辑有点 incorrect - 棘手的部分是您正在检查 flang 和 20,25 但 else if 位于末尾从来没有达到那个点。

带 '10', '15', '20', '25' 的 threaded 选项放在第一个 if 处，因此无论 condition 是否匹配 [=26]，它总是变成 true =]

此外，您还需要在 HTML 中使用 onchange 函数而不是 onclick 函数。 onchange函数用于改变selection或checkboxes。

实时工作演示：（全部按要求工作）

$(document).ready(function() {
  var list1 = document.getElementById('firstList');
  list1.options[1] = new Option('Thread/Solder', 'Thread/Solder');
  list1.options[2] = new Option('Flange/Groove', 'Flange/Groove');
});

function getValveSize() {
  var list1 = document.getElementById('firstList');
  var list2 = document.getElementById("secondList");
  var list1SelectedValue = list1.options[list1.selectedIndex].value;

  if (list1SelectedValue === 'Thread/Solder') {

    list2.options.length = 0;
    list2.options[0] = new Option('DN', '');
    list2.options[1] = new Option('10', '10');
    list2.options[2] = new Option('15', '15');
    list2.options[3] = new Option('20', '20');
    list2.options[4] = new Option('25', '25');
    list2.options[5] = new Option('32', '32');
    list2.options[6] = new Option('40', '40');
    list2.options[7] = new Option('50', '50');
    list2.options[8] = new Option('65', '65');

  } else if (list1SelectedValue === 'Flange/Groove') {

    list2.options.length = 0;
    list2.options[0] = new Option('DN', '');
    list2.options[1] = new Option('20', '20');
    list2.options[2] = new Option('25', '25');
    list2.options[3] = new Option('32', '32');
    list2.options[4] = new Option('40', '40');
    list2.options[5] = new Option('50', '50');
    list2.options[6] = new Option('65', '65');
    list2.options[7] = new Option('80', '80');
    list2.options[8] = new Option('100', '100');
    list2.options[9] = new Option('125', '125');
    list2.options[10] = new Option('150', '150');
    list2.options[11] = new Option('200', '200');
    list2.options[12] = new Option('250', '250');
    list2.options[13] = new Option('300', '300');
    list2.options[14] = new Option('350', '350');
    list2.options[15] = new Option('400', '400');
  }
}

function getTurns() {
  var list1 = document.getElementById('firstList');
  var list2 = document.getElementById('secondList');
  var list3 = document.getElementById('thirdList');
  var list1SelectedValue = list1.options[list1.selectedIndex].value;
  var list2SelectedValue = list2.options[list2.selectedIndex].value;

  if (list1SelectedValue == 'Flange/Groove' && $.inArray(list2SelectedValue, ['20', '25']) >= 0) {
    list3.options.length = 0;
    list3.options[0] = new Option('1', '1');
    list3.options[1] = new Option('1.1', '1.1');
    list3.options[2] = new Option('1.2', '1.2');
    list3.options[3] = new Option('1.3', '1.3');
    list3.options[4] = new Option('1.4', '1.4');
    list3.options[5] = new Option('1.5', '1.5');
    list3.options[6] = new Option('1.6', '1.6');
    list3.options[7] = new Option('1.7', '1.7');
    list3.options[8] = new Option('1.8', '1.8');
    list3.options[8] = new Option('1.9', '1.9');
    list3.options[9] = new Option('2', '2');
    list3.options[10] = new Option('2.1', '2.1');
    list3.options[11] = new Option('2.2', '2.2');
    list3.options[12] = new Option('2.3', '2.3');
    list3.options[13] = new Option('2.4', '2.4');
    list3.options[14] = new Option('2.5', '2.5');
    list3.options[15] = new Option('2.6', '2.6');
    list3.options[16] = new Option('2.7', '2.7');
    list3.options[17] = new Option('2.8', '2.8');
    list3.options[18] = new Option('2.9', '2.9');
    list3.options[19] = new Option('3', '3');
    list3.options[20] = new Option('3.1', '3.1');
    list3.options[21] = new Option('3.2', '3.2');
    list3.options[22] = new Option('3.3', '3.3');
    list3.options[23] = new Option('3.4', '3.4');
    list3.options[24] = new Option('3.5', '3.5');
    list3.options[25] = new Option('3.6', '3.6');
    list3.options[26] = new Option('3.7', '3.7');
    list3.options[27] = new Option('3.8', '3.8');
    list3.options[28] = new Option('3.9', '3.9');
    list3.options[29] = new Option('4', '4');
    list3.options[30] = new Option('4.1', '4.1');
    list3.options[31] = new Option('4.2', '4.2');
    list3.options[32] = new Option('4.3', '4.3');
    list3.options[33] = new Option('4.4', '4.4');
    list3.options[34] = new Option('4.5', '4.5');
    list3.options[35] = new Option('4.6', '4.6');
    list3.options[36] = new Option('4.7', '4.7');
    list3.options[37] = new Option('4.8', '4.8');
    list3.options[38] = new Option('4.9', '4.9');
    list3.options[39] = new Option('5', '5');
    list3.options[40] = new Option('5.1', '5.1');
    list3.options[41] = new Option('5.2', '5.2');
    list3.options[42] = new Option('5.3', '5.3');
    list3.options[43] = new Option('5.4', '5.4');
    list3.options[44] = new Option('5.5', '5.5');
    list3.options[45] = new Option('5.6', '5.6');
    list3.options[46] = new Option('5.7', '5.7');
    list3.options[47] = new Option('5.8', '5.8');
    list3.options[48] = new Option('5.9', '5.9');
    list3.options[49] = new Option('6', '6');
    list3.options[50] = new Option('6.1', '6.1');
    list3.options[51] = new Option('6.2', '6.2');
    list3.options[52] = new Option('6.3', '6.3');
    list3.options[53] = new Option('6.4', '6.4');
    list3.options[54] = new Option('6.5', '6.5');
    list3.options[55] = new Option('6.6', '6.6');
    list3.options[56] = new Option('6.7', '6.7');
    list3.options[57] = new Option('6.8', '6.8');
    list3.options[58] = new Option('6.9', '6.9');
    list3.options[59] = new Option('7', '7');
  } else if ($.inArray(list2SelectedValue, ['32', '40', '50']) >= 0) {
    list3.options.length = 0;
    list3.options[0] = new Option('Turns', '');
    list3.options[1] = new Option('0.25', '0.25');
    list3.options[2] = new Option('0.5', '0.5');
    list3.options[3] = new Option('0.75', '0.75');
    list3.options[4] = new Option('1', '1');
    list3.options[5] = new Option('1.1', '1.1');
    list3.options[6] = new Option('1.2', '1.2');
    list3.options[7] = new Option('1.3', '1.3');
    list3.options[8] = new Option('1.4', '1.4');
    list3.options[9] = new Option('1.5', '1.5');
    list3.options[10] = new Option('1.6', '1.6');
    list3.options[11] = new Option('1.7', '1.7');
    list3.options[12] = new Option('1.8', '1.8');
    list3.options[13] = new Option('1.9', '1.9');
    list3.options[14] = new Option('2', '2');
    list3.options[15] = new Option('2.1', '2.1');
    list3.options[16] = new Option('2.2', '2.2');
    list3.options[17] = new Option('2.3', '2.3');
    list3.options[18] = new Option('2.4', '2.4');
    list3.options[19] = new Option('2.5', '2.5');
    list3.options[20] = new Option('2.6', '2.6');
    list3.options[21] = new Option('2.7', '2.7');
    list3.options[22] = new Option('2.8', '2.8');
    list3.options[23] = new Option('2.9', '2.9');
    list3.options[24] = new Option('3', '3');
    list3.options[25] = new Option('3.1', '3.1');
    list3.options[26] = new Option('3.2', '3.2');
    list3.options[27] = new Option('3.3', '3.3');
    list3.options[28] = new Option('3.4', '3.4');
    list3.options[29] = new Option('3.5', '3.5');
    list3.options[30] = new Option('3.6', '3.6');
    list3.options[31] = new Option('3.7', '3.7');
    list3.options[32] = new Option('3.8', '3.8');
    list3.options[33] = new Option('3.9', '3.9');
    list3.options[34] = new Option('4', '4');
    list3.options[35] = new Option('4.1', '4.1');
    list3.options[36] = new Option('4.2', '4.2');
    list3.options[37] = new Option('4.3', '4.3');
    list3.options[38] = new Option('4.4', '4.4');
    list3.options[39] = new Option('4.5', '4.5');
    list3.options[40] = new Option('4.6', '4.6');
    list3.options[41] = new Option('4.7', '4.7');
    list3.options[42] = new Option('4.8', '4.8');
    list3.options[43] = new Option('4.9', '4.9');
    list3.options[44] = new Option('5', '5');
    list3.options[45] = new Option('5.1', '5.1');
    list3.options[46] = new Option('5.2', '5.2');
    list3.options[47] = new Option('5.3', '5.3');
    list3.options[48] = new Option('5.4', '5.4');
    list3.options[49] = new Option('5.5', '5.5');
    list3.options[50] = new Option('5.6', '5.6');
    list3.options[51] = new Option('5.7', '5.7');
    list3.options[52] = new Option('5.8', '5.8');
    list3.options[53] = new Option('5.9', '5.9');
    list3.options[54] = new Option('6', '6');
    list3.options[55] = new Option('6.1', '6.1');
    list3.options[56] = new Option('6.2', '6.2');
    list3.options[57] = new Option('6.3', '6.3');
    list3.options[58] = new Option('6.4', '6.4');
    list3.options[59] = new Option('6.5', '6.5');
    list3.options[60] = new Option('6.6', '6.6');
    list3.options[61] = new Option('6.7', '6.7');
    list3.options[62] = new Option('6.8', '6.8');
    list3.options[63] = new Option('6.9', '6.9');
    list3.options[64] = new Option('7', '7');
    list3.options[65] = new Option('7.1', '7.1');
    list3.options[66] = new Option('7.2', '7.2');
    list3.options[67] = new Option('7.3', '7.3');
    list3.options[68] = new Option('7.4', '7.4');
    list3.options[69] = new Option('7.5', '7.5');
    list3.options[70] = new Option('7.6', '7.6');
    list3.options[71] = new Option('7.7', '7.7');
    list3.options[72] = new Option('7.8', '7.8');
    list3.options[73] = new Option('7.9', '7.9');
    list3.options[74] = new Option('8', '8');
    list3.options[75] = new Option('8.1', '8.1');
    list3.options[76] = new Option('8.2', '8.2');
    list3.options[77] = new Option('8.3', '8.3');
    list3.options[78] = new Option('8.4', '8.4');
    list3.options[79] = new Option('8.5', '8.5');
    list3.options[80] = new Option('8.6', '8.6');
    list3.options[81] = new Option('8.7', '8.7');
    list3.options[82] = new Option('8.8', '8.8');
    list3.options[83] = new Option('8.9', '8.9');
    list3.options[84] = new Option('9', '9');
    list3.options[85] = new Option('9.1', '9.1');
    list3.options[86] = new Option('9.2', '9.2');
    list3.options[87] = new Option('9.3', '9.3');
    list3.options[88] = new Option('9.4', '9.4');
    list3.options[89] = new Option('9.5', '9.5');
    list3.options[90] = new Option('9.6', '9.6');
    list3.options[91] = new Option('9.7', '9.7');
    list3.options[92] = new Option('9.8', '9.8');
    list3.options[93] = new Option('9.9', '9.9');
    list3.options[94] = new Option('10', '10');
  } else if ($.inArray(list2SelectedValue, ['65']) >= 0) {
    list3.options.length = 0;
    list3.options[0] = new Option('1', '1');
    list3.options[1] = new Option('1.1', '1.1');
    list3.options[2] = new Option('1.2', '1.2');
    list3.options[3] = new Option('1.3', '1.3');
    list3.options[4] = new Option('1.4', '1.4');
    list3.options[5] = new Option('1.5', '1.5');
    list3.options[6] = new Option('1.6', '1.6');
    list3.options[7] = new Option('1.7', '1.7');
    list3.options[8] = new Option('1.8', '1.8');
    list3.options[9] = new Option('1.9', '1.9');
    list3.options[10] = new Option('2', '2');
    list3.options[11] = new Option('2.1', '2.1');
    list3.options[12] = new Option('2.2', '2.2');
    list3.options[13] = new Option('2.3', '2.3');
    list3.options[14] = new Option('2.4', '2.4');
    list3.options[15] = new Option('2.5', '2.5');
    list3.options[16] = new Option('2.6', '2.6');
    list3.options[17] = new Option('2.7', '2.7');
    list3.options[18] = new Option('2.8', '2.8');
    list3.options[19] = new Option('2.9', '2.9');
    list3.options[20] = new Option('3', '3');
    list3.options[21] = new Option('3.1', '3.1');
    list3.options[22] = new Option('3.2', '3.2');
    list3.options[23] = new Option('3.3', '3.3');
    list3.options[24] = new Option('3.4', '3.4');
    list3.options[25] = new Option('3.5', '3.5');
    list3.options[26] = new Option('3.6', '3.6');
    list3.options[27] = new Option('3.7', '3.7');
    list3.options[28] = new Option('3.8', '3.8');
    list3.options[29] = new Option('3.9', '3.9');
    list3.options[30] = new Option('4', '4');
    list3.options[31] = new Option('4.1', '4.1');
    list3.options[32] = new Option('4.2', '4.2');
    list3.options[33] = new Option('4.3', '4.3');
    list3.options[34] = new Option('4.4', '4.4');
    list3.options[35] = new Option('4.5', '4.5');
    list3.options[36] = new Option('4.6', '4.6');
    list3.options[37] = new Option('4.7', '4.7');
    list3.options[38] = new Option('4.8', '4.8');
    list3.options[39] = new Option('4.9', '4.9');
    list3.options[40] = new Option('5', '5');
    list3.options[41] = new Option('5.1', '5.1');
    list3.options[42] = new Option('5.2', '5.2');
    list3.options[43] = new Option('5.3', '5.3');
    list3.options[44] = new Option('5.4', '5.4');
    list3.options[45] = new Option('5.5', '5.5');
    list3.options[46] = new Option('5.6', '5.6');
    list3.options[47] = new Option('5.7', '5.7');
    list3.options[48] = new Option('5.8', '5.8');
    list3.options[49] = new Option('5.9', '5.9');
    list3.options[50] = new Option('6', '6');
    list3.options[51] = new Option('6.1', '6.1');
    list3.options[52] = new Option('6.2', '6.2');
    list3.options[53] = new Option('6.3', '6.3');
    list3.options[54] = new Option('6.4', '6.4');
    list3.options[55] = new Option('6.5', '6.5');
    list3.options[56] = new Option('6.6', '6.6');
    list3.options[57] = new Option('6.7', '6.7');
    list3.options[58] = new Option('6.8', '6.8');
    list3.options[59] = new Option('6.9', '6.9');
    list3.options[60] = new Option('7', '7');
    list3.options[61] = new Option('7.1', '7.1');
    list3.options[62] = new Option('7.2', '7.2');
    list3.options[63] = new Option('7.3', '7.3');
    list3.options[64] = new Option('7.4', '7.4');
    list3.options[65] = new Option('7.5', '7.5');
    list3.options[66] = new Option('7.6', '7.6');
    list3.options[67] = new Option('7.7', '7.7');
    list3.options[68] = new Option('7.8', '7.8');
    list3.options[69] = new Option('7.9', '7.9');
    list3.options[70] = new Option('8', '8');
    list3.options[71] = new Option('8.1', '8.1');
    list3.options[72] = new Option('8.2', '8.2');
    list3.options[73] = new Option('8.3', '8.3');
    list3.options[74] = new Option('8.4', '8.4');
    list3.options[75] = new Option('8.5', '8.5');
    list3.options[76] = new Option('8.6', '8.6');
    list3.options[77] = new Option('8.7', '8.7');
    list3.options[78] = new Option('8.8', '8.8');
    list3.options[79] = new Option('8.9', '8.9');
    list3.options[80] = new Option('9', '9');
    list3.options[81] = new Option('9.1', '9.1');
    list3.options[82] = new Option('9.2', '9.2');
    list3.options[83] = new Option('9.3', '9.3');
    list3.options[84] = new Option('9.4', '9.4');
    list3.options[85] = new Option('9.5', '9.5');
    list3.options[86] = new Option('9.6', '9.6');
    list3.options[87] = new Option('9.7', '9.7');
    list3.options[88] = new Option('9.8', '9.8');
    list3.options[89] = new Option('9.9', '9.9');
    list3.options[90] = new Option('10', '10');
    list3.options[91] = new Option('10.1', '10.1');
    list3.options[92] = new Option('10.2', '10.2');
    list3.options[93] = new Option('10.3', '10.3');
    list3.options[94] = new Option('10.4', '10.4');
    list3.options[95] = new Option('10.5', '10.5');
    list3.options[96] = new Option('10.6', '10.6');
    list3.options[97] = new Option('10.7', '10.7');
    list3.options[98] = new Option('10.8', '10.8');
    list3.options[99] = new Option('10.9', '10.9');
    list3.options[100] = new Option('11', '11');
    list3.options[101] = new Option('11.1', '11.1');
    list3.options[102] = new Option('11.2', '11.2');
    list3.options[103] = new Option('11.3', '11.3');
    list3.options[104] = new Option('11.4', '11.4');
    list3.options[105] = new Option('11.5', '11.5');
    list3.options[106] = new Option('11.6', '11.6');
    list3.options[107] = new Option('11.7', '11.7');
    list3.options[108] = new Option('11.8', '11.8');
    list3.options[109] = new Option('11.9', '11.9');
    list3.options[110] = new Option('12', '12');
  } else if ($.inArray(list2SelectedValue, ['10', '15', '20', '25']) >= 0) {
    list3.options.length = 0;
    list3.options[0] = new Option('Turns', '');
    list3.options[1] = new Option('0.25', '0.25');
    list3.options[2] = new Option('0.5', '0.5');
    list3.options[3] = new Option('0.75', '0.75');
    list3.options[4] = new Option('1', '1');
    list3.options[5] = new Option('1.1', '1.1');
    list3.options[6] = new Option('1.2', '1.2');
    list3.options[7] = new Option('1.3', '1.3');
    list3.options[8] = new Option('1.4', '1.4');
    list3.options[9] = new Option('1.5', '1.5');
    list3.options[10] = new Option('1.6', '1.6');
    list3.options[11] = new Option('1.7', '1.7');
    list3.options[12] = new Option('1.8', '1.8');
    list3.options[13] = new Option('1.9', '1.9');
    list3.options[14] = new Option('2', '2');
    list3.options[15] = new Option('2.1', '2.1');
    list3.options[16] = new Option('2.2', '2.2');
    list3.options[17] = new Option('2.3', '2.3');
    list3.options[18] = new Option('2.4', '2.4');
    list3.options[19] = new Option('2.5', '2.5');
    list3.options[20] = new Option('2.6', '2.6');
    list3.options[21] = new Option('2.7', '2.7');
    list3.options[22] = new Option('2.8', '2.8');
    list3.options[23] = new Option('2.9', '2.9');
    list3.options[24] = new Option('3', '3');
    list3.options[25] = new Option('3.1', '3.1');
    list3.options[26] = new Option('3.2', '3.2');
    list3.options[27] = new Option('3.3', '3.3');
    list3.options[28] = new Option('3.4', '3.4');
    list3.options[29] = new Option('3.5', '3.5');
    list3.options[30] = new Option('3.6', '3.6');
    list3.options[31] = new Option('3.7', '3.7');
    list3.options[32] = new Option('3.8', '3.8');
    list3.options[33] = new Option('3.9', '3.9');
    list3.options[34] = new Option('4', '4');
    list3.options[35] = new Option('4.1', '4.1');
    list3.options[36] = new Option('4.2', '4.2');
    list3.options[37] = new Option('4.3', '4.3');
    list3.options[38] = new Option('4.4', '4.4');
    list3.options[39] = new Option('4.5', '4.5');
    list3.options[40] = new Option("4.6", "4.6");
    list3.options[41] = new Option("4.7", "4.7");
    list3.options[42] = new Option("4.8", "4.8");
    list3.options[43] = new Option("4.9", "4.9");
    list3.options[44] = new Option("5", "5");
    list3.options[45] = new Option("5.1", "5.1");
    list3.options[46] = new Option("5.2", "5.2");
    list3.options[47] = new Option("5.3", "5.3");
    list3.options[48] = new Option("5.4", "5.4");
    list3.options[49] = new Option("5.5", "5.5");
    list3.options[50] = new Option("5.6", "5.6");
    list3.options[51] = new Option("5.7", "5.7");
    list3.options[52] = new Option("5.8", "5.8");
    list3.options[53] = new Option("5.9", "5.9");
    list3.options[54] = new Option("6", "6");
    list3.options[55] = new Option("6.1", "6.1");
    list3.options[56] = new Option("6.2", "6.2");
    list3.options[57] = new Option("6.3", "6.3");
    list3.options[58] = new Option("6.4", "6.4");
    list3.options[59] = new Option("6.5", "6.5");
    list3.options[60] = new Option("6.6", "6.6");
    list3.options[61] = new Option("6.7", "6.7");
    list3.options[62] = new Option("6.8", "6.8");
    list3.options[63] = new Option("6.9", "6.9");
    list3.options[64] = new Option("7", "7");
  }
  $('#thirdList').append(list3);
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="valvetype">
  <select class="form-control" id='firstList' name='firstList' onchange="getValveSize()">
    <option disabled selected>Choose</option>
  </select>
  <select class="form-control" id='secondList' name='secondList' onchange="getTurns()">
    <option disabled selected>DN</option>
  </select>
  <select class="form-control" id='thirdList' name='thirdList'>
    <option disabled selected>Turns</option>
  </select>
  <button onclick="findInArray()" class="submit">Submit</button>
</div>

根据其他选择更改动态添加的下拉菜单的选项

Alter options on dynamically added drop down menu based on other selections

javascript

jquery

dropdown