Populate one dropdown list based on another dropdown list

Question

I have two dropdown menus as follows:

<form id="dynamicForm">
  <select id="A">

  </select>
  <select id="B">

  </select>
</form>

And I have a dictionary object where the keys are the options for A and the values, B are arrays corresponding to each element in A , as follows:

var diction = {
    A1: ["B1", "B2", "B3"], 
    A2: ["B4", "B5", "B6"]
}

How can I dynamically populate the menu B based on what the user selects in menu A?

Answer 1

Bind a change event handler and populate second select tag based on selected value.

 var diction = { A1: ["B1", "B2", "B3"], A2: ["B4", "B5", "B6"] } // bind change event handler $('#A').change(function() { // get the second dropdown $('#B').html( // get array by the selected value diction[this.value] // iterate and generate options .map(function(v) { // generate options with the array element return $('<option/>', { value: v, text: v }) }) ) // trigger change event to generate second select tag initially }).change() 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <form id="dynamicForm"> <select id="A"> <option value="A1">A1</option> <option value="A2">A2</option> </select> <select id="B"> </select> </form> 

Answer 2

You can create a change listener for the first select box and populate the html of the second select box.

See demo below:

 var diction = { A1: ["B1", "B2", "B3"], A2: ["B4", "B5", "B6"] } $('#A').on('change', function() { $('#B').html( diction[$(this).val()].reduce(function(p, c) { return p.concat('<option value="' + c + '">' + c + '</option>'); }, '') ); }).trigger('change'); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <form id="dynamicForm"> <select id="A"> <option value="A1">A1</option> <option value="A2">A2</option> </select> <select id="B"> </select> </form> 

Answer 3

This will dynamically populate both select s:

 var diction = { A1: ["B1", "B2", "B3"], A2: ["B4", "B5", "B6"] }; // the function that will populate the select function populateSelect(id, values) { // get the select element var $select = $(id); // empty it $select.empty(); // for each value in values ... values.forEach(function(value) { // create an option element var $option = $("<option value='" + value + "'>" + value + "</option>"); // and append it to the select $select.append($option); }); } // when the #A select changes ... $("#A").on("change", function() { // get the value of the selected element (the key) var key = $(this).val(); // populate #B accordingly populateSelect("#B", diction[key]); }); // Before anything, populate #A with the keys of diction and ... populateSelect("#A", Object.keys(diction)); // ... #B with whatever #A hold its key populateSelect("#B", diction[$("#A").val()]); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <form id="dynamicForm"> <select id="A"> </select> <select id="B"> </select> </form>