Passing extra arguments to XMLHttpRequest.onload

Question

I'm trying to comunicate with a server, using XMLHttpRequest in javascript.

How can I pass info to the onload function?

// global variable that containts server response
var reply;

var makeRequest = function(extraInfo) {
  var request = new XMLHttpRequest();
  request.open(...);
  request.onload = handler;
};

var handler = function(data) {
  reply = data.target.response;
  console.log("Server Reply: " + reply);
};

How can I pass the parameter extraInfo from makeRequest to the handler function? (without using a global variable)

Answer 1

Just use a closure in such way:

...
var makeRequest = function(extraInfo) {
    var request = new XMLHttpRequest();
    request.open(...);
    request.onload = function(data) {
        // extraInfo is accessible here
        reply = data.target.response;
        console.log("Server Reply: " + reply);
    };
};

Answer 2

I figured out that passing extra info into the request handler can be done this way: (At least is good for me)

    request.open(...);
    request.extraInfo = identifier;
    request.onload = function() {
        identifier = this.extraInfo;
    };