jquery - 获取选择输入中所选选项的值

I'm quite a newbie when it comes to jquery. I'm using cakePHP and I have a form to register orders for a selected user, the select input for selecting the user looks like this in cakePHP:

echo $this->Form->input('user_id');

and that renders a form with an input like this:

<label for="OrderUserId">User</label>
<select name="data[Order][user_id]" id="OrderUserId">
    <option value="2"> User 2</option>
    <option value="3"> User 3</option>
</select>

I want to do an ajax call so that, when a user is selected, his info appears in a div. So far, I have this javascript:

$(document).ready(function(){
    $("#OrderUserId").change(function() {
        $.ajax({
            url: 'users/getData' //here would go the user ID
        });
    });
});

My question is this: how can I get the value of the selected option with jQuery so that I can pass it to the url in the ajax method?

Just use plain js this.value. this inside your callback represents the dom element so you would just access its value using .value.

$(document).ready(function(){
    $("#OrderUserId").change(function() {
         //var user = this.value;
        $.ajax({
            url: 'users/getData/' + this.value //here would go the user ID
        });
    });
});

Fiddle

$(document).ready(function(){
    $("#OrderUserId").change(function() {
        var _this=$(this);
        $.ajax({
            url: 'users/getData'+_this.val(); //here would go the user ID
        });
    });
});