jQuery onchange选择选项

Question

Let's say I have this HTML:

<select id='list'>
    <option value='1'>First</option>
    <option value='2'>Second</option>
    <option value='3'>Third </option>
</select> 
<input type ="text" id="text"/>

and then this JavaScript

 //other variables are also declared here
    var x1 = 5;
    var x2 = 10;
    var value = x1 * x2;
    var list_value =$("#list").change(function() {
             $(this).val();
 // just an example of how i want the function in the variable 
    });
    var nwval = value * list_value;
      $('#text').val(nwval);
// some long piece of code 
// i'm also using the list_value value somewhere in the long piece of code..

I want the val in the textbox to change as the user selects an option, I know it'll work if I wrap the change event around it, but is there any way to go about this while keeping it as that variable list_value ?

Answer 1

var x1 = 5;
var x2 = 10;
var value = x1 * x2;
var nwval;
$("#list").change(function() {
    nwval = value * $(this).val();
    $('#text').val(nwval);
});

Answer 2

$('#text').val($('option:selected').text());
$('#list').change(function(){

        $('#text').val($('option:selected').text());
})

check from here http://jsfiddle.net/QrHUN/

Answer 3

Wrapping the change event is the better way as it creates a closure, you could use global variables as below, but you would be better (imho) to simply grab the value again futher down.

You could technically do (although a bad idea as it is global variables):

var x1 = 5;
var x2 = 10;
var value = x1 * x2;
var list_value = 1;
$("#list").change(function() {
    list_value = $(this).val();
    var nwval = value * list_value;
    $('#text').val(nwval); 
});

Answer 4

this returns a jQuery object, not a value.

var list_value =$("#list").change(function() {  

If you want the value outside of the code, you would need to do something like this

var list_value = 0;
var sel = $("#list").change(function() {
         list_value = $(this).val();
}).change();
var nwval = value * list_value;
$('#text').val(nwval);

BUT the onchange event will never update the page, just that variable!