How to write data from Form in HTML to XML with Javascript

Question

This is an assignment from my class. What I need to do is create a registration page. When the user presses the submit button, I have take all the information on the form an

Answer 1

By the way, my Professor purposely did not teach us how to do this because he wants us to research on it by ourselves.

Which should give you a hint about searching a bit more deeply. Anyhow, I'm not going to comment on every line, but I will offer some hints.

 var xmlDoc = new ActiveXObject("Microsoft.XMLDOM");

That is a Microsoft proprietary way of creating an XML document and it is normally wrapped in try..catch as different ActiveXObjects are provided in different versions of IE. You also need to look for document.implementation.createDocument.

    //DEFINE LOAD METHOD
    function LoadXML(xmlFile)
    {
     xmlDoc.load(xmlFile);

You might want to check out the async parameter.

     xmlObj = xmlDoc.documentElement;
    }

    //declare & initialize array
    var arrPerson = new Array();

It is considered better practice to use an array literal: ... = [];

    //initialize array w/ xml
    function initialize_array()
    {
    LoadXML("PersonXML.xml");
    var x = 0;
    while (x < xmlObj.childNodes.length)

Getting the length of xmlObj.childNodes on every loop is inefficient, consider storing the length and comparing with that value.

    {
        var tmpArr = new Array(xmlObj.childNodes(x).getAttribute("Usrname"), 
                               xmlObj.childNodes(x).getAttribute("Pswd"), 
                               xmlObj.childNodes(x).getAttribute("FirstName"), 
                               xmlObj.childNodes(x).getAttribute("LastName"), 
                               xmlObj.childNodes(x).getAttribute("DOB"),
                               xmlObj.childNodes(x).getAttribute("Gender"),  
                               xmlObj.childNodes(x).getAttribute("Title"));

It is very inefficient to access xmlObj.childNodes(x) repeatedly. Store a reference and reuse it.

        arrPerson.push(tmpArr);

You could assign the values directly to arrPerson and get rid of tmpArr.

        x++;   

Using a plain for loop will increment x for you.

    }
    }

    //Validation
    function LogInVal(objtxt)
    {
        if(objtxt.value.length == 0)
        {
            objtxt.style.background = "red";
            return 1;
        }

        else
        {
            objtxt.style.background = "white";
            return 0;
        }
    }

Not all browsers will let you style the background color of input elements.

    //main validation
    function MainVal(objForm)
    {
        var errmsg = "empty field";
        var errmsg2 = "Incorrect Username and Password";

You might want a better way of naming the error messages and relating them to other information for that message. An object might do the job.

        var msg = "You have logged in successfully";
        var errCount = 0;

        var usrn = document.getElementById("usrname1").value;
        var pswd = document.getElementById("pswd1").value;

        errCount += LogInVal(objForm.usrname);
        errCount/*1*/ += LogInVal(objForm.pswd);

        initialize_array();    

        if (errCount != 0)
        {
            alert(errmsg);
            return false;
        }
        else if(authentication(usrn, pswd) == true)

The function authentication() returns true or false, so you don't need to compare it to anything, you can just test the returned value (i.e. there is no need for == true above).

        {

            alert(msg);
            return true;
            setCookie('invalidUsr',' ttttt');
        }
        else
        {
            alert(errmsg2);
            return false;
        }
    }

Instead of showing alert messages one at a time in an alert, consider putting them in the document adjacent to the elements they relate to. That way the user can see the messaeg while fixing the error.