[javascript code]
var varname = varvalue; //Declaring your variable is not mandatory, but good practice.

[javascript code]
var variable1 = 1; //Declare a variable.
if(variable1 == 1){ 
	// Increment variable value by 1
	variable1++;
	/* The following brings up a message box, a handy way of checking variable values as you
	 	   		go. Be careful not to use these in loops that are too long. */
	alert(variable1); 
}else if(variable1 == 2){ //Elseif's in javascript require a space between the else and if.
	for(i=0;i<20;i++){ //For loop.
		variable1++;
	}
    	switch(variable1){ //Switch conditional
       		case 22:
           		alert("variable 1 has value of 22!");
           		break; 
       		default:
           		alert("didn't have value of 22!");
			break;
	}
}else{
	alert('The final else statement');
}

[javascript code]
function functioname(argument1, argument2, argument3){
	/* Arguments not provided will be null */
	if(argument3 == null){
		return argument1 + argument2
	}else{
		return argument1 + argument2 + argument3
	}
}

/* And call it with */
alert(functionname(1, 2)); //returns 3
/* or */
alert(functionname(1, 2, 3)); //returns 6

[javascript code]
var request_o = new ActiveXObject("Microsoft.XMLHTTP");

[javascript code]
var request_o = new XMLHttpRequest();

[javascript code]
/* The following function creates an XMLHttpRequest object... */

function createRequestObject(){
	var request_o; //declare the variable to hold the object.
	var browser = navigator.appName; //find the browser name
	if(browser == "Microsoft Internet Explorer"){
		/* Create the object using MSIE's method */
		request_o = new ActiveXObject("Microsoft.XMLHTTP");
	}else{
		/* Create the object using other browser's method */
		request_o = new XMLHttpRequest();
	}
	return request_o; //return the object
}

/* You can get more specific with version information by using 
	parseInt(navigator.appVersion)
	Which will extract an integer value containing the version 
	of the browser being used.
*/
	

[javascript code]

/* The variable http will hold our new XMLHttpRequest object. */
var http = createRequestObject(); 

/* Function called to get the product categories list */
function getProducts(){
	/* Create the request. The first argument to the open function is the method (POST/GET),
		and the second argument is the url... 
		document contains references to all items on the page
		We can reference document.form_category_select.select_category_select and we will
		be referencing the dropdown list. The selectedIndex property will give us the 
		index of the selected item. 
	*/
	http.open('get', 'internal_request.php?action=get_products&id=' 
			+ document.form_category_select.select_category_select.selectedIndex);
	/* Define a function to call once a response has been received. This will be our
		handleProductCategories function that we define below. */
	http.onreadystatechange = handleProducts; 
	/* Send the data. We use something other than null when we are sending using the POST
		method. */
	http.send(null);
}

/* Function called to handle the list that was returned from the internal_request.php file.. */
function handleProducts(){
	/* Make sure that the transaction has finished. The XMLHttpRequest object 
		has a property called readyState with several states:
		0: Uninitialized
		1: Loading
		2: Loaded
		3: Interactive
		4: Finished */
	if(http.readyState == 4){ //Finished loading the response
		/* We have got the response from the server-side script,
			let's see just what it was. using the responseText property of 
			the XMLHttpRequest object. */
		var response = http.responseText;
		/* And now we want to change the product_categories <div> content.
			we do this using an ability to get/change the content of a page element 
			that we can find: innerHTML. */
		document.getElementById('product_cage').innerHTML = response;
	}
}

	http.abort;
	http.open('post',  'back_end.php');
	http.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
	http.send('arg1=val1&arg2=val2&arg3=val3');

/* Reference the product_list element to the variable product_list */
product_list = XMLReponse.getElementByTagName('product_id');

/* By substituting product_list for XMLResponse, we will be searching
	only the product_list element, not the entire response 
	We also use getElementsByTagName, not getElementByTagName, 
	since we are interested in all of the results, not just one. */

product_id = XMLResponse.getElementsByTagName('product');

/* getElementsByTagName produces an array, which we can access  like this:
	product_id[n], the same way we access an array item in PHP. 
	Let's get the id attribute from the product elements like this: */

for(i=0; i<product_id.length; i++){ //length is the same as count($array)
	id = product_id[i].getAttribute('id') //Grabs the id attribute.
	/* To get the text from within a text node, we use firstChild.data
		for the corresponding element. */
	name = product_id[i].getElementByTagName('name').firstChild.data;
	version = product_id[i].getElementByTagName('version').firstChild.data;
}