选择框上的jQuery AJAX

Question

I'm trying to use ajax on a select box and change html elements with matching id's on event of change in select box. I have a code like below but it does not seem to work and rather generates 'Uncaught ReferenceError: data is not defined'

Below is the code that I am using. Is there something wrong with this?

$('#PolicyCategory').live('change',function(){
    var policy = $('#PolicyCategory').val();
    var form_data = {
        category_id: policy,
        ajax: '1'       
    };

    console.log();
    alert(data.conn);

    $.ajax({
        url: "http://coverbuddy.favstay.com/users/category_ajax",
        type: "POST",
        dataType: "json",
        cache: false,
        data: form_data,
        success: function(data){
            alert(data);
        }
    });
});

Answer 1

这意味着变量data未在脚本中定义，而是在这里引起的：

 alert(data.conn);

Answer 2

The error comes up from

alert(data.conn);

Where you don't have defined variable data as far as we can see from your code. Remove this line or define the variable before you use it.

Answer 3

You try to to use data where it is not defined: alert(data.conn); , which naturally gives you the error

Answer 4

Yes you need to write the " alert(data.conn);" with in the success function..

$('#PolicyCategory').live('change',function(){
    var policy = $('#PolicyCategory').val();
    var form_data = {
        category_id: policy,
        ajax: '1'       
    };
    console.log();


    $.ajax({
        url: "http://coverbuddy.favstay.com/users/category_ajax",
        type: "POST",
        dataType: "json",
        cache: false,
        data : form_data,
        success: function(data){
            alert(data);
            alert(data.conn);
        }
    });
});

Answer 5

that's because of the alert(data.conn);

remove it and it will work