jquery: if-statement for var in dropdown-menu

Question

I applied a replacement for a dropdown-menu and the jQuery replacement stays empty because the preselected value of the select-option-form is undefined (the values are generated dynamically). When I click the replacement and choose an option it works as it should. Here is the excerpt of the replacement code I think it is responsible for the error:

function createDropDownSF(){
  var searchForm_type = $("#searchForm_type");
  var selected = searchForm_type.find("option[selected]");
  var options = $("option", searchForm_type);

Therefore I tried to extend the function with this code, to make the function use the first option available when there is no selected value, but it doesn't work:

if (selected.is("undefined")) {
    searchForm_type.find("option")[0];
}

Does anyone has an idea?

Answer 1

I would first try to get a list off al the options that are selected and check if the length > 0.

 $("select option:selected").length > 0

Then you can use JQuery to select the first option.

$('select option').first().attr('selected', true);

Answer 2

Did you mean it that way?

function createDropDownSF(){
  var searchForm_type = $("#searchForm_type");
  var selected = searchForm_type.find("option[selected]");
        $("select option:selected").length > 0;
        $('select option').first().attr('selected', true);
  var options = $("option", searchForm_type);

Answer 3

<select id="test">
<option>1</option>
<option>2</option>
<option selected="selected">3</option>
<option>4</option>

$(function () {

    if ($("#test option:selected").length > 0) {
        // something is selected
        alert("selected");
    } else {
        // nothing is selected
        $('#test option').first().attr('selected', true);
    }
});

I don't know how to set the select that is doesn't have a value selected, but this code should work.