[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 <a href="http://www.phpbuilder.com/columns/internal_request.php">internal_request.php file</a>.. */
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;
}