What is the best way to add options to a select from a JavaScript object with jQuery?

What is the best method for adding options to a <select> from a JavaScript object using jQuery?

I'm looking for something that I don't need a plugin to do, but I would also be interested in the plugins that are out there.

This is what I did:

selectValues = { "1": "test 1", "2": "test 2" };

for (key in selectValues) {
  if (typeof (selectValues[key] == 'string') {
    $('#mySelect').append('<option value="' + key + '">' + selectValues[key] + '</option>');
  }
}

A clean/simple solution:

This is a cleaned up and simplified version of matdumsa's:

$.each(selectValues, function(key, value) {
     $('#mySelect')
          .append($('<option>', { value : key })
          .text(value));
});

Changes from matdumsa's: (1) removed the close tag for the option inside append() and (2) moved the properties/attributes into an map as the second parameter of append().

The same as other answers, in a jQuery fashion:

$.each(selectValues, function(key, value) {   
     $('#mySelect')
         .append($("<option></option>")
                    .attr("value", key)
                    .text(value)); 
});

var output = [];

$.each(selectValues, function(key, value)
{
  output.push('<option value="'+ key +'">'+ value +'</option>');
});

$('#mySelect').html(output.join(''));

In this way you "touch the DOM" only one time.

I'm not sure if the latest line can be converted into $('#mySelect').html(output.join('')) because I don't know jQuery internals (maybe it does some parsing in the html() method)

This is slightly faster and cleaner.

var selectValues = {
  "1": "test 1",
  "2": "test 2"
};
var $mySelect = $('#mySelect');
//
$.each(selectValues, function(key, value) {
  var $option = $("<option/>", {
    value: key,
    text: value
  });
  $mySelect.append($option);
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<select id="mySelect"></select>

jQuery

var list = $("#selectList");
$.each(items, function(index, item) {
  list.append(new Option(item.text, item.value));
});

Vanilla JavaScript

var list = document.getElementById("selectList");
for(var i in items) {
  list.add(new Option(items[i].text, items[i].value));
}

If you don't have to support old IE versions, using the Option constructor is clearly the way to go, a readable and efficient solution:

$(new Option('myText', 'val')).appendTo('#mySelect');

It's equivalent in functionality to, but cleaner than:

$("<option></option>").attr("value", "val").text("myText")).appendTo('#mySelect');