javascript - how to substract options two related selects html -

if have 3 units available , 2 selects hhtml select quantity, how can when client select 1 unit (option value=1) example in first select, option substract in second select, , show remaining units? ie, second select show 1 unit (option value=1) , 2 units (option value=2).i dont need show , hide. need if client select 1 unit in first select, in second can select 2 more. options value refers quantity

<select class="quantity" name="double room"> <option value="1">1</option> <option value="2">2</option <option value="3">3</option </select> <p> <select class="quantity" name="double room"> <option value="1">1</option> <option value="2">2</option <option value="3">3</option </select> 

here quick solution, point in right direction. doesn't fancy preserve order, removes , returns options on second select.

https://jsfiddle.net/jpbjd40s/2/

// intialize value option missing #two var previousvalue = 1;  // stuff on change. $('#one').on('change', function() {      // put unselected option #one in #two.     $('#two').append('<option value="' + previousvalue + '">' + previousvalue + '</option>');      // remember had.     previousvalue = $('#one').val();      // remove option #two selected in #one.     $('#two').children('[value="' + $('#one').val() + '"]').remove();  });