The first example is a closure. It only operates when the $.post function is completed. If you just tried to use the alert(data) as you have in the second example it would execute right away.
A closure is the equivalent to burying a time-capsule in the ground to be dug up later. You could leave the box open and the stuff in it lying around, but then it wouldn't be valuable, would it? What you do is close the box up and put it away until the time is right to look inside it. Then when the time comes (after the $.post), it is dug up and the contents examined. Try reading this, it's accessible and the examples are fairly easy to understand... http://blog.morrisjohns.com/javascript_closures_for_dummies Don't worry if you don't get it right away, that just means you're a mere mortal. Eric On Jul 11, 9:40 pm, james_027 <[EMAIL PROTECTED]> wrote: > Hi, > > I am using $.post() function, I don't understand what is callback > function ... > > what is the difference between > > $.post('test.cgi', params, > function(data) { > alert(data); > } > ); > > and > > $.post('test.cgi', params, alert(data)); > > the data being shown is different. and I don't seem to understand what > is the difference in function(data) {alert(data);} from alert(data). > For me function(data) {alert(data);} is just a function taking the > data and just passing it to the alert(). Is function() inside the > $.post something special? where does the data come from? are the data > in the function(data) {alert(data);} and alert(data) different? > > Thanks > james
