JavaScript: Passing parameters to a callback function

This would also work:

// callback function
function tryMe(param1, param2) {
  alert(param1 + " and " + param2);
}

// callback executer 
function callbackTester(callback) {
  callback();
}

// test function
callbackTester(function() {
  tryMe("hello", "goodbye");
});

Another Scenario :

// callback function
function tryMe(param1, param2, param3) {
  alert(param1 + " and " + param2 + " " + param3);
}

// callback executer 
function callbackTester(callback) {
  //this is the more obivous scenario as we use callback function
  //only when we have some missing value
  //get this data from ajax or compute
  var extraParam = "this data was missing";

  //call the callback when we have the data
  callback(extraParam);
}

// test function
callbackTester(function(k) {
  tryMe("hello", "goodbye", k);
});

If you are not sure how many parameters are you going to be passed into callback functions, use apply function.

function tryMe (param1, param2) {
  alert (param1 + " and " + param2);
}

function callbackTester(callback,params){
    callback.apply(this,params);
}

callbackTester(tryMe,['hello','goodbye']);

If you want something slightly more general, you can use the arguments variable like so:

function tryMe(param1, param2) {
  alert(param1 + " and " + param2);
}

function callbackTester(callback) {
  callback(arguments[1], arguments[2]);
}

callbackTester(tryMe, "hello", "goodbye");

But otherwise, your example works fine (arguments[0] can be used in place of callback in the tester)

Your question is unclear. If you're asking how you can do this in a simpler way, you should take a look at the ECMAScript 5th edition method .bind(), which is a member of Function.prototype. Using it, you can do something like this:

function tryMe (param1, param2) {
    alert (param1 + " and " + param2);
}

function callbackTester (callback) {
    callback();
}

callbackTester(tryMe.bind(null, "hello", "goodbye"));

You can also use the following code, which adds the method if it isn't available in the current browser:

// From Prototype.js
if (!Function.prototype.bind) { // check if native implementation available
  Function.prototype.bind = function(){ 
    var fn = this, args = Array.prototype.slice.call(arguments),
        object = args.shift(); 
    return function(){ 
      return fn.apply(object, 
        args.concat(Array.prototype.slice.call(arguments))); 
    }; 
  };
}

Example

bind() - PrototypeJS Documentation