JavaScript - Calculating A Person's Age

// JavaScript Document

var tblRows = 20;
var tblColumns = 10;
var tblArray = new Array(tblRows);
var p = window.parent;

// Initial page event handler
function initPage() 
{
    p.refAssignCellFromTextbox = assignCellFromTextbox;

    for (var i = 0; i < tblArray.length; i++) 
	{
        tblArray[i] = new Array(tblColumns);
        for (var j = 0; j < tblArray[i].length; j++)
            tblArray[i][j] = "0";
    }

    recalculate();
}

// Recalculate cell values
function recalculate() 
{
    for (var i = 0; i < tblRows; i++) 
	{
        for (var j = 0; j < tblColumns; j++) 
		{
            if (tblArray[i][j].indexOf("=SUM") != -1) 
			{
                calculateCell(i, j);            
            }
        }
    }
}

// Click cell event handler
function clickCell(cellRef) 
{
    thisRef = cellRef;
	
    var cellID = cellRef.id;

    var row = parseFloat(cellID.substr(0, 3)) - 1;
    var column = parseFloat(cellID.substr(3, 2)) - 1;

    var cellValue = tblArray[row][column];
    var tokenArray = getFormula(cellValue);

    if (tokenArray != null)
        p.assignTextboxFromArray(cellValue);
    else
        p.assignTextboxFromCell(cellRef);
}

// Update cell from textbox
function assignCellFromTextbox(tblValue) 
{
    if (thisRef != undefined) 
	{
        if (tblValue == "") 
		{
            tblValue = "0";
        }
        var tokenArray = getFormula(tblValue);

        if (tokenArray != null) 
		{
            assignArray(thisRef.id, tblValue.toUpperCase());
        }
        else 
		{
            if (!isFloat(tblValue)) 
			{
                    parseValue = tblValue.replace(/[^0-9]/g, '');
                    tblValue = parseValue;
            }
            assignArray(thisRef.id, tblValue);
            if (tblValue == "0")
                thisRef.innerText = "";
            else
                thisRef.innerText = tblValue;
        }
		
        recalculate();
    }
}

// Determines if a user entered a formula
function getFormula(tblValue) 
{
    var pattern = /[:|\(|\)]/;
    var ar = tblValue.split(pattern);
    var sum = ar[0].toUpperCase();

    if (ar.length < 3)
        return null;
    else if (sum != "=SUM") 
	{
        return null;
    }
    else 
	{
        return ar;
    }
}

function assignArray(cellID, tblValue) 
{
    var row = parseFloat(cellID.substr(0, 3));
    var column = parseFloat(cellID.substr(3, 2));

    tblArray[row - 1][column - 1] = tblValue;
}

function calculateCell(row, column)
{
    var tokenArray = getFormula(tblArray[row][column]);

    if (tokenArray != null) 
	{
        var fromColumn = tokenArray[1].substr(0, 1);
        var fromRow = tokenArray[1].substr(1, tokenArray[1].length - 1);

        var toColumn = tokenArray[2].substr(0, 1);
        var toRow = tokenArray[2].substr(1, tokenArray[2].length - 1);

        var fromRowIndex = parseFloat(fromRow) - 1;
        var fromColIndex = fromColumn.charCodeAt(0) - 65;

        var toRowIndex = parseFloat(toRow) - 1;
        var toColIndex = toColumn.charCodeAt(0) - 65;

        var sumTotal = 0;

        for (var i = fromRowIndex; i <= toRowIndex; i++) 
		{
            for (var j = fromColIndex; j <= toColIndex; j++) 
			{
                if (isFloat(tblArray[i][j]))
                    sumTotal += parseFloat(tblArray[i][j]);
            }
        }

        var cellID = fillField((row + 1).toString(), 3) + fillField((column + 1).toString(), 2);
        document.getElementById(cellID).innerText = sumTotal;
    }
}

function isFloat(s) 
{
    var ch = "";
    var justFloat = "0123456789.";

    for (var i = 0; i < s.length; i++) 
	{
        ch = s.substr(i, 1);
        if (justFloat.indexOf(ch) == -1)
            return false;
    }
    return true;
}

function fillField(s,n)
{
    var zeros = "0000000000";
    return zeros.substring(0, n - s.length) + s;
}

// JavaScript Document

var refAssignCellFromTextbox;
var nCharsAllowed = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890.=(): ";


// Event Handler
function initPage() 
{
    document.getElementById("TableFrame").style.top = "50px";
    document.getElementById("TableFrame").src = "tablepage.html";
}

// Updates text field when a user clicks on a particular field from with the spreadsheet
function assignTextboxFromCell(cValue) 
{
    document.getElementById("fieldEntry").value = cValue.innerText;
    document.getElementById("fieldEntry").focus();
}

// Assists tablepage.js with updating a value from a 2D array
function assignTextboxFromArray(aValue) 
{
    document.getElementById("fieldEntry").value = aValue;
    document.getElementById("fieldEntry").focus();
}

// Used when a user presses a key to update text field
function filterText() 
{
    if (window.event.keyCode != 13) 
	{
        if (!nCharOK(window.event.keyCode))
            window.event.keyCode = null;
    }
    else 
	{
        window.event.keyCode = null;
        refAssignCellFromTextbox(document.getElementById("fieldEntry").value);
    }
}

// Checks to see if character entered falls within our preset
function nCharOK(c) 
{
    var ch = (String.fromCharCode(c));
    ch = ch.toUpperCase();

    if (nCharsAllowed.indexOf(ch) != -1)
        return true;
    else
        return false;
}

// Clears all data from the screen
function clearPage() 
{
    initPage();
    document.getElementById("fieldEntry").value = "";
}

// Add a row to the table
function addRow(frmTable) 
{
	var table = document.getElementById(frmTable);
	var rowCount = table.rows.length;
	var row = table.insertRow(rowCount);
	var cell1 = row.insertCell(0);
	// cell2.innerHTML = rowCount + 1;
	// Unless this is going to be completely dynamic
	// the rest of the table code would have had to be 
	// entered in statically. Not happening.
}

// Delete a row from the table
function deleteRow(frmTable) 
{
	try 
	{
		var table = document.getElementById(frmTable);
		var rowCount = table.rows.length;

		for(var i=0; i<rowCount; i++) 
		{
			var row = table.rows[i];
			var chkbox = row.cells[0].childNodes[0];
			if(null != chkbox && true == chkbox.checked) 
			{
				table.deleteRow(i);
				rowCount--;
				i--;
			}
		}
	}
	catch(e) 
	{
		alert(e);
	}
}