Dynamically select Drop Down in Jquery

Question

I have 4 Drop Downs.

Each drop by default has a --select-- option. Each box has a unique id. As you can see, the second drop down is disabled if the above drop

Answer 1

Rather than hiding the options, I would use the disable attribute (comments in code):

var selects = $('.drop-down');
selects.not(':eq(0)').prop('disabled', true); // disable all but first drop down

selects.on('change', function() {
  var select = $(this),
      currentIndex = selects.index(select),
      nextIndex = currentIndex + 1;
  
  // only do this if it is not last select
  if (currentIndex != selects.length - 1) { 
    selects.slice(nextIndex)        // get all selects after current one
           .val('')                 // reset value
           .prop('disabled', true); // disable 
    
    selects.eq(nextIndex).prop('disabled', select.val() === ''); // disable / enable next select based on val
  }
  
})

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select class="drop-down">
  <option value="">--Select--</option>
  <option value="1">1</option>
  <option value="2">2</option>
  <option value="3">3</option>
  <option value="4">4</option>
</select><br>
<select class="drop-down">
  <option value="">--Select--</option>
  <option value="1">1</option>
  <option value="2">2</option>
  <option value="3">3</option>
  <option value="4">4</option>
</select><br>
<select class="drop-down">
  <option value="">--Select--</option>
  <option value="1">1</option>
  <option value="2">2</option>
  <option value="3">3</option>
  <option value="4">4</option>
</select><br>
<select class="drop-down">
  <option value="">--Select--</option>
  <option value="1">1</option>
  <option value="2">2</option>
  <option value="3">3</option>
  <option value="4">4</option>
</select>

Answer 2

Assuming the option that has '--select--' as text has no value, just use val on the handler to check if the selected option is other than the empty

if(this.val() !== '') {
// enable following select
}

Answer 3

Check this one;

HTML code:

<select id="sel-1"></select>
<select id="sel-2"></select>
<select id="sel-3"></select>
<select id="sel-4"></select>

JS Code:

$(document).ready(function(){

     $("[id^=sel]").change(function(){

           /*
           *  find out the current box id
           */

           var id=$(this).attr("id");
           /*
           *  find out the current box id order number
           */

           var ordernumber=id.split("-")[1];

           if($(this).val()!="select")
           {
                 //enable next one
                 $("#sel-"+(ordernumber+1)).show();
           }
     })
})

Answer 4

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<style>
  select {
    margin: 5px 0;
    display: block;
  }
</style>
<script>
  $(function() {
    $('.cls-select').change(function() {

      if ($(this).val() == '--select--') {

        // reset and disable the next drop downs
        $('.cls-select:gt(' + $('.cls-select').index($(this)) + ')').val('--select--').prop('disabled', true)

      } else {

        // current drop down has value so enable the next drop down
        $(this).next().prop('disabled', false);
      }
    });
  })
</script>

<select class="cls-select">
  <option>--select--</option>
  <option>one</option>
  <option>two</option>
</select>
<select class="cls-select" disabled>
  <option>--select--</option>
  <option>one</option>
  <option>two</option>
</select>
<select class="cls-select" disabled>
  <option>--select--</option>
  <option>one</option>
  <option>two</option>
</select>
<select class="cls-select" disabled>
  <option>--select--</option>
  <option>one</option>
  <option>two</option>
</select>