how to pre-select a dropdown options which are dynamically generating?

Question

I am getting the select dropdown options from the server, and i have stored a value in a variable in javascript. If the options are matching to the value i am having that will be preselected in the select dropdown. Below is my code.

this is to get the dropdown options from server and append to select dropdown.

$.ajax({
        type: "GET",
        url: '/enquiry/user',
         dataSrc: "data",
         dataType : 'json',
        cache: false,
        success: function(users){
            var mySelect = $('#assigned');
    $.each(users, function(index, options){
      console.log(options._id);
       mySelect.append(
    $('<option></option>').val(options._id).html(options.firstName)
);
        // $('#assigned').append('<option value="'+users._id+'">'+users.firstName+'</option>');
    });

and here i am having a value in a variable f8 = document.getElementById('assigned');

If the value in f8 matches to the options, that option should get pre-selected.

Iam using materialize CSS

Html dropdown <select id="assigned"> <option value="">Change Assignee</option> </select>

Answer 1

$('#optionID').prop('selected',true)

//to update material select component per materializecss doc
$('#select').material_select('destroy')
$('#select').material_select()

working fiddle here , though not ajax request, but dynamically generated options

edit:

$('#select').append($('<option></option>').val(VALUE).html(HTML))
$('#select').val(SELECTED_VALUE)
$('#select').material_select('destroy')
$('#select').material_select()