Directly returning a value through ajax

[bonecone]

I'm attempting to simplify my javascript code when it comes to ajax, but afterwords it only prints 'undefined' to the screen rather than what I want it to print.

I want to be able to put something like this on my main page
onclick="document.getElementById('output').innerHTML = print_output();"
where print_output() is the ajax function. This way I don't have to use a function to assign values directly to innerHTML and I don't have to muck about with a js file whenever I want to change my page layout.

To do this, I created a recursive function:

function print_output(return_value) {

	// if a value has been passed to the function, simply return it
	if(return_value || return_value == 0) {
		return return_value;
	}

	// otherwise call the response object
	else {
		http = getHTTPObject();

		// recursively calls the first function once the
		// text has been received
		http.onreadystatechange = function() {
			if(http.readyState == 4 && http.status == 200) {
				print_output(http.responseText);
			}
		}

		url = "index.php";
		params = "output=Ajax is working properly";

		http.open("POST", url, true);
		http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
		http.setRequestHeader("Content-length", params.length);
		http.setRequestHeader("Connection", "close");
		http.send(params);
	}
}

but like I said, it prints 'undefined' out to the screen. Why isn't this printing the contents that it receives from 'index.php' like it's supposed to?

[bonecone]

Found the solution afterwords. For anyone interested, I reworked the code like this:

function print_output(return_value) {

	// if a value has been passed to the function, simply return it
	if(return_value || return_value == 0) {
		return return_value;
	}

	// otherwise call the response object
	else {
		http = getHTTPObject();

		url = "index.php";
		params = "output=Ajax is working properly";

		http.open("POST", url, false);
		http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
		http.setRequestHeader("Content-length", params.length);
		http.setRequestHeader("Connection", "close");
		http.send(params);
		return http.responseText;
	}
}