How can I bind an event on a selectedIndex changed on <select> element?

By using jQuery how do I attach an event on the following select element so that on index change it alerts "I have changed!"?

<select id="selCars">
  <option>Volvo</option>
  <option>Saab</option>
  <option>Mercedes</op开发者_如何学运维tion>
  <option>Audi</option>
</select>

Use the onchange event. When the selectionIndex of the <select> element changes, the change event is fired.

Execute this piece of code after the element is created. If you want to add the on load, wrap it in a $(document).ready(function(){ ... }) , abbreviated by $(function(){...})

$("#selCars").change(function(){
    // Do something...
    //this refers to the `<select>` element
    var newoption = $(this)
    var selectedOption = $("option:selected", this);

    //Example: 
    alert("I have changed!");
})

$(function(){  
   $("#selCars").change(function() {
       alert("I have changed!");
   });
}); 

$("#selCars").change(function() {
    alert("I have changed!");
});

$('#selCars').change(function(){
    alert( "I have changed!" );
})