临时记录

1. (function () {
2.  
   var previous;
3.  
    
4.  
   $("select").on('focus', function () {
5.  
   // Store the current value on focus and on change
6.  
   previous = this.value;
7.  
   }).change(function() {
8.  
   // Do something with the previous value after the change
9.  
   alert(previous);
10.  
     
11.  
    // Make sure the previous value is updated
12.  
    previous = this.value;
13.  
    });
14.  
    })();