How do I change selected value of select2 dropdown with JqGrid?

For select2 version >= 4.0.0

The other solutions might not work, however the following examples should work.

Solution 1: Causes all attached change events to trigger, including select2

$('select').val('1').trigger('change');

Solution 2: Causes JUST select2 change event to trigger

$('select').val('1').trigger('change.select2');

See this jsfiddle for examples of these. Thanks to @minlare for Solution 2.

Explanation:

Say I have a best friend select with people's names. So Bob, Bill and John (in this example I assume the Value is the same as the name). First I initialize select2 on my select:

$('#my-best-friend').select2();

Now I manually select Bob in the browser. Next Bob does something naughty and I don't like him anymore. So the system unselects Bob for me:

$('#my-best-friend').val('').trigger('change');

Or say I make the system select the next in the list instead of Bob:

// I have assume you can write code to select the next guy in the list
$('#my-best-friend').val('Bill').trigger('change');  

Notes on Select 2 website (see Deprecated and removed methods) that might be useful for others:

.select2('val') The "val" method has been deprecated and will be removed in Select2 4.1. The deprecated method no longer includes the triggerChange parameter.

You should directly call .val on the underlying element instead. If you needed the second parameter (triggerChange), you should also call .trigger("change") on the element.

$('select').val('1').trigger('change'); // instead of $('select').select2('val', '1');

Looking at the select2 docs you use the below to get/set the value.

$("#select").select2("val"); //get the value
$("#select").select2("val", "CA"); //set the value

@PanPipes has pointed out that this has changed for 4.x (go toss him an upvote below). val is now called directly

$("#select").val("CA");

So within the loadComplete of the jqGrid you can get whatever value you are looking for then set the selectbox value.

Notice from the docs

Notice that in order to use this method you must define the initSelection function in the options so Select2 knows how to transform the id of the object you pass in val() to the full object it needs to render selection. If you are attaching to a select element this function is already provided for you.