How to transfer another parameter with an ajax state change

I have the following code in my ajax query:

xhr.onreadystatechange = stateChange;

and the function stateChange is function stateChange(event)

Is it possible to add a second parameter to the function so it doesn't just passes a number as well as the event?

I've tried doing xhr.onreadystatechange = stateChange(event,'123'); with function stateChange(event,num) but it doesn't seem t开发者_JAVA技巧o work.

You can create a closure that allows your event handling function access to those variables.

Instead of

xhr.blahblah;
xhr.onreadystatechange = stateChange;
xhr.blahblah;

This technique creates an anonymous function that gives scope to your '123' variable:

xhr.blahblah;
function (xhrObj, callbackFn, param) {
  xhrObj.onreadystatechange = function (event) {
    callbackFn(event, param);
  };
}(xhr, stateChange, '123');
xhr.blahblah;

Mmmm, sort of:

xhr.onreadystatechange = function(event) { stateChange(event,'123'); };

would do what you say you want, but it isn't clear to me that what you say you want is what you need.