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How to invoke a postback from clientside javascript?

Collindsouza asked
Medium Priority
Last Modified: 2008-01-09
Hi Experts,

I have a datepicker control with a onclick event that runs client side which i invoke by calling the displayDatePicker function. This function pops up up a monthly calender to the textbox assigned for that date picker.. namely  'ctl00$ContentPlaceHolder1$DtRespAlerted'

the code for this is as follows

<input id="DtRespAlerted" class="DtTextBox" type="text" name="DtRespAlerted" runat="server" onfocus="setdate2(this,15)" onchange="setdate2(this,15)" />
<img src="images/Calender.jpg" alt="Calender" onclick="displayDatePicker('ctl00$ContentPlaceHolder1$DtRespAlerted');" />

I also have 2 events.. namely onfocus and onchange event for the textbox which passes the current date and adds 15 days to the current date and displays the new date to another text box.. the function is as follows

    <script type="text/javascript">
        function parseInt2(n){ n=n.replace(/[^0-9]/,'').replace(/^0/,'');return n?parseInt(n):0;}
        function setdate2(o,daysExtra)
          var a=o.value.split('/'),d=parseInt2(a[0]),m=parseInt2(a[1])-1,y=parseInt2(a[2]),dt=new Date(y,m,d);
          var MM = dt.getMonth()+1;
          var DD = dt.getDate();
          var YYYY = dt.getFullYear();


So far so good..
The problem i've got is... While adding 15 days to the given date.. I need to consider weekends and any given bank holidays.. what i mean by this is... that I need to calculate only working days and exclude weekends and bank holidays..
For example if todays date is the 1st of November.. Adding 15 working days should give me 27th of November..

The bank holidays are stored in a table in the database.. I have a stored procedure that calculates this for me.. it takes into account weekends and bank holidays while calculating the next working date.. i.e (Given date + no of days)

i somehow need to fire a post back event immideatly after the onclick="displayDatePicker('ctl00$ContentPlaceHolder1$DtRespAlerted');"  is clicked

the display displayDatePicker function is in a js file..

the code is as follows...

var datePickerDivID = "datepicker";
var iFrameDivID = "datepickeriframe";

var dayArrayShort = new Array('Su', 'Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa');
var dayArrayMed = new Array('Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat');
var dayArrayLong = new Array('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday');
var monthArrayShort = new Array('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
var monthArrayMed = new Array('Jan', 'Feb', 'Mar', 'Apr', 'May', 'June', 'July', 'Aug', 'Sept', 'Oct', 'Nov', 'Dec');
var monthArrayLong = new Array('January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December');
// these variables define the date formatting we're expecting and outputting.
// If you want to use a different format by default, change the defaultDateSeparator
// and defaultDateFormat variables either here or on your HTML page.
var defaultDateSeparator = "/";        // common values would be "/" or "."
var defaultDateFormat = "dmy"    // valid values are "mdy", "dmy", and "ymd"
var dateSeparator = defaultDateSeparator;
var dateFormat = defaultDateFormat;

This is the main function you'll call from the onClick event of a button.
Normally, you'll have something like this on your HTML page:

Start Date: <input name="StartDate">
<input type=button value="select" onclick="displayDatePicker('StartDate');">

That will cause the datepicker to be displayed beneath the StartDate field and
any date that is chosen will update the value of that field. If you'd rather have the
datepicker display beneath the button that was clicked, you can code the button
like this:

<input type=button value="select" onclick="displayDatePicker('StartDate', this);">

So, pretty much, the first argument (dateFieldName) is a string representing the
name of the field that will be modified if the user picks a date, and the second
argument (displayBelowThisObject) is optional and represents an actual node
on the HTML document that the datepicker should be displayed below.

In version 1.1 of this code, the dtFormat and dtSep variables were added, allowing
you to use a specific date format or date separator for a given call to this function.
Normally, you'll just want to set these defaults globally with the defaultDateSeparator
and defaultDateFormat variables, but it doesn't hurt anything to add them as optional
parameters here. An example of use is:

<input type=button value="select" onclick="displayDatePicker('StartDate', false, 'dmy', '.');">

This would display the datepicker beneath the StartDate field (because the
displayBelowThisObject parameter was false), and update the StartDate field with
the chosen value of the datepicker using a date format of dd.mm.yyyy
function displayDatePicker(dateFieldName, displayBelowThisObject, dtFormat, dtSep)
  var targetDateField = document.getElementsByName (dateFieldName).item(0);
  // if we weren't told what node to display the datepicker beneath, just display it
  // beneath the date field we're updating
  if (!displayBelowThisObject)
    displayBelowThisObject = targetDateField;
  // if a date separator character was given, update the dateSeparator variable
  if (dtSep)
    dateSeparator = dtSep;
    dateSeparator = defaultDateSeparator;
  // if a date format was given, update the dateFormat variable
  if (dtFormat)
    dateFormat = dtFormat;
    dateFormat = defaultDateFormat;
  var x = displayBelowThisObject.offsetLeft;
  var y = displayBelowThisObject.offsetTop + displayBelowThisObject.offsetHeight ;
  // deal with elements inside tables and such
  var parent = displayBelowThisObject;
  while (parent.offsetParent) {
    parent = parent.offsetParent;
    x += parent.offsetLeft;
    y += parent.offsetTop ;
  drawDatePicker(targetDateField, x, y);

Draw the datepicker object (which is just a table with calendar elements) at the
specified x and y coordinates, using the targetDateField object as the input tag
that will ultimately be populated with a date.

This function will normally be called by the displayDatePicker function.
function drawDatePicker(targetDateField, x, y)
  var dt = getFieldDate(targetDateField.value );
  // the datepicker table will be drawn inside of a <div> with an ID defined by the
  // global datePickerDivID variable. If such a div doesn't yet exist on the HTML
  // document we're working with, add one.
  if (!document.getElementById(datePickerDivID)) {
    // don't use innerHTML to update the body, because it can cause global variables
    // that are currently pointing to objects on the page to have bad references
    //document.body.innerHTML += "<div id='" + datePickerDivID + "' class='dpDiv'></div>";
    var newNode = document.createElement("div");
    newNode.setAttribute("id", datePickerDivID);
    newNode.setAttribute("class", "dpDiv");
    newNode.setAttribute("style", "visibility: hidden;");
  // move the datepicker div to the proper x,y coordinate and toggle the visiblity
  var pickerDiv = document.getElementById(datePickerDivID);
  pickerDiv.style.position = "absolute";
  pickerDiv.style.left = x + "px";
  pickerDiv.style.top = y + "px";
  pickerDiv.style.visibility = (pickerDiv.style.visibility == "visible" ? "hidden" : "visible");
  pickerDiv.style.display = (pickerDiv.style.display == "block" ? "none" : "block");
  pickerDiv.style.zIndex = 10000;
  // draw the datepicker table
  refreshDatePicker(targetDateField.name, dt.getFullYear(), dt.getMonth(), dt.getDate());

This is the function that actually draws the datepicker calendar.
function refreshDatePicker(dateFieldName, year, month, day)
  // if no arguments are passed, use today's date; otherwise, month and year
  // are required (if a day is passed, it will be highlighted later)
  var thisDay = new Date();
  if ((month >= 0) && (year > 0)) {
    thisDay = new Date(year, month, 1);
  } else {
    day = thisDay.getDate();
  // the calendar will be drawn as a table
  // you can customize the table elements with a global CSS style sheet,
  // or by hardcoding style and formatting elements below
  var crlf = "\r\n";
  var TABLE = "<table cols=7 class='dpTable'>" + crlf;
  var xTABLE = "</table>" + crlf;
  var TR = "<tr class='dpTR'>";
  var TR_title = "<tr class='dpTitleTR'>";
  var TR_days = "<tr class='dpDayTR'>";
  var TR_todaybutton = "<tr class='dpTodayButtonTR'>";
  var xTR = "</tr>" + crlf;
  var TD = "<td class='dpTD' onMouseOut='this.className=\"dpTD\";' onMouseOver=' this.className=\"dpTDHover\";' ";    // leave this tag open, because we'll be adding an onClick event
  var TD_title = "<td colspan=5 class='dpTitleTD'>";
  var TD_buttons = "<td class='dpButtonTD'>";
  var TD_todaybutton = "<td colspan=7 class='dpTodayButtonTD'>";
  var TD_days = "<td class='dpDayTD'>";
  var TD_selected = "<td class='dpDayHighlightTD' onMouseOut='this.className=\"dpDayHighlightTD\";' onMouseOver='this.className=\"dpTDHover\";' ";    // leave this tag open, because we'll be adding an onClick event
  var xTD = "</td>" + crlf;
  var DIV_title = "<div class='dpTitleText'>";
  var DIV_selected = "<div class='dpDayHighlight'>";
  var xDIV = "</div>";
  // start generating the code for the calendar table
  var html = TABLE;
  // this is the title bar, which displays the month and the buttons to
  // go back to a previous month or forward to the next month
  html += TR_title;
  html += TD_buttons + getButtonCode(dateFieldName, thisDay, -1, "&lt;") + xTD;
  html += TD_title + DIV_title + monthArrayLong[ thisDay.getMonth()] + " " + thisDay.getFullYear() + xDIV + xTD;
  html += TD_buttons + getButtonCode(dateFieldName, thisDay, 1, "&gt;") + xTD;
  html += xTR;
  // this is the row that indicates which day of the week we're on
  html += TR_days;
  for(i = 0; i < dayArrayShort.length; i++)
    html += TD_days + dayArrayShort[i] + xTD;
  html += xTR;
  // now we'll start populating the table with days of the month
  html += TR;
  // first, the leading blanks
  for (i = 0; i < thisDay.getDay(); i++)
    html += TD + "&nbsp;" + xTD;
  // now, the days of the month
  do {
    dayNum = thisDay.getDate();
    var dow = thisDay.getDay();
    TD_onclick = "";
    if  ( dow > 0 && dow < 6 ) {
      TD_onclick = " onclick=\"updateDateField('" + dateFieldName + "', '" + getDateString(thisDay) + "');\"";
    TD_onclick += ">";

//Code commented to disable display selection of weekend dates
  //do {
    //dayNum = thisDay.getDate();
   // TD_onclick = " onclick=\"updateDateField('" + dateFieldName + "', '" + getDateString(thisDay) + "');\">";
    if (dayNum == day)
      html += TD_selected + TD_onclick + DIV_selected + dayNum + xDIV + xTD;
      html += TD + TD_onclick + dayNum + xTD;
    // if this is a Saturday, start a new row
    if (thisDay.getDay() == 6)
      html += xTR + TR;
    // increment the day
    thisDay.setDate(thisDay.getDate() + 1);
  } while (thisDay.getDate() > 1)
  // fill in any trailing blanks
  if (thisDay.getDay() > 0) {
    for (i = 6; i > thisDay.getDay(); i--)
      html += TD + "&nbsp;" + xTD;
  html += xTR;
  // add a button to allow the user to easily return to today, or close the calendar
  var today = new Date();
  var todayString = "Today is " + dayArrayMed[today.getDay()] + ", " + monthArrayMed[ today.getMonth()] + " " + today.getDate();
  html += TR_todaybutton + TD_todaybutton;
  html += "<button class='dpTodayButton' onClick='refreshDatePicker(\"" + dateFieldName + "\");'>this month</button> ";
  html += "<button class='dpTodayButton' onClick='updateDateField(\"" + dateFieldName + "\");'>close</button>";
  html += xTD + xTR;
  // and finally, close the table
  html += xTABLE;
  document.getElementById(datePickerDivID).innerHTML = html;
  // add an "iFrame shim" to allow the datepicker to display above selection lists

Convenience function for writing the code for the buttons that bring us back or forward
a month.
function getButtonCode(dateFieldName, dateVal, adjust, label)
  var newMonth = (dateVal.getMonth () + adjust) % 12;
  var newYear = dateVal.getFullYear() + parseInt((dateVal.getMonth() + adjust) / 12);
  if (newMonth < 0) {
    newMonth += 12;
    newYear += -1;
  return "<button class='dpButton' onClick='refreshDatePicker(\"" + dateFieldName + "\", " + newYear + ", " + newMonth + ");'>" + label + "</button>";

Convert a JavaScript Date object to a string, based on the dateFormat and dateSeparator
variables at the beginning of this script library.
function getDateString(dateVal)
  var dayString = "00" + dateVal.getDate();
  var monthString = "00" + (dateVal.getMonth()+1);
  dayString = dayString.substring(dayString.length - 2);
  monthString = monthString.substring(monthString.length - 2);
  switch (dateFormat) {
    case "dmy" :
      return dayString + dateSeparator + monthString + dateSeparator + dateVal.getFullYear();
    case "ymd" :
      return dateVal.getFullYear() + dateSeparator + monthString + dateSeparator + dayString;
    case "mdy" :
    default :
      return monthString + dateSeparator + dayString + dateSeparator + dateVal.getFullYear();

Convert a string to a JavaScript Date object.
function getFieldDate(dateString)
  var dateVal;
  var dArray;
  var d, m, y;
  try {
    dArray = splitDateString(dateString);
    if (dArray) {
      switch (dateFormat) {
        case "dmy" :
          d = parseInt(dArray[0], 10);
          m = parseInt(dArray[1], 10) - 1;
          y = parseInt(dArray[2], 10);
        case "ymd" :
          d = parseInt(dArray[2], 10);
          m = parseInt(dArray[1], 10) - 1;
          y = parseInt(dArray[0], 10);
        case "mdy" :
        default :
          d = parseInt(dArray[1], 10);
          m = parseInt(dArray[0], 10) - 1;
          y = parseInt(dArray[2], 10);
      dateVal = new Date(y, m, d);
    } else if (dateString) {
      dateVal = new Date(dateString);
    } else {
      dateVal = new Date();
  } catch(e) {
    dateVal = new Date();
  return dateVal;

Try to split a date string into an array of elements, using common date separators.
If the date is split, an array is returned; otherwise, we just return false.
function splitDateString(dateString)
  var dArray;
  if (dateString.indexOf("/") >= 0)
    dArray = dateString.split("/");
  else if (dateString.indexOf(".") >= 0)
    dArray = dateString.split(".");
  else if (dateString.indexOf("-") >= 0)
    dArray = dateString.split("-");
  else if (dateString.indexOf("\\") >= 0)
    dArray = dateString.split("\\");
    dArray = false;
  return dArray;

Update the field with the given dateFieldName with the dateString that has been passed,
and hide the datepicker. If no dateString is passed, just close the datepicker without
changing the field value.

Also, if the page developer has defined a function called datePickerClosed anywhere on
the page or in an imported library, we will attempt to run that function with the updated
field as a parameter. This can be used for such things as date validation, setting default
values for related fields, etc. For example, you might have a function like this to validate
a start date field:

function datePickerClosed(dateField)
  var dateObj = getFieldDate(dateField.value);
  var today = new Date();
  today = new Date(today.getFullYear(), today.getMonth(), today.getDate());
  if (dateField.name == "StartDate") {
    if (dateObj < today) {
      // if the date is before today, alert the user and display the datepicker again
      alert("Please enter a date that is today or later");
      dateField.value = "";
      document.getElementById(datePickerDivID).style.visibility = "visible";
    } else {
      // if the date is okay, set the EndDate field to 7 days after the StartDate
      dateObj.setTime(dateObj.getTime() + (7 * 24 * 60 * 60 * 1000));
      var endDateField = document.getElementsByName ("EndDate").item(0);
      endDateField.value = getDateString(dateObj);

function updateDateField(dateFieldName, dateString)
  var targetDateField = document.getElementsByName (dateFieldName).item(0);
  if (dateString)
    targetDateField.value = dateString;
  var pickerDiv = document.getElementById(datePickerDivID);
  pickerDiv.style.visibility = "hidden";
  pickerDiv.style.display = "none";
  // after the datepicker has closed, optionally run a user-defined function called
  // datePickerClosed, passing the field that was just updated as a parameter
  // (note that this will only run if the user actually selected a date from the datepicker)
  if ((dateString) && (typeof(datePickerClosed) == "function"))

Use an "iFrame shim" to deal with problems where the datepicker shows up behind
selection list elements, if they're below the datepicker. The problem and solution are
described at:

function adjustiFrame(pickerDiv, iFrameDiv)
  // we know that Opera doesn't like something about this, so if we
  // think we're using Opera, don't even try
  var is_opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
  if (is_opera)
  // put a try/catch block around the whole thing, just in case
  try {
    if (!document.getElementById(iFrameDivID)) {
      // don't use innerHTML to update the body, because it can cause global variables
      // that are currently pointing to objects on the page to have bad references
      //document.body.innerHTML += "<iframe id='" + iFrameDivID + "' src='javascript:false;' scrolling='no' frameborder='0'>";
      var newNode = document.createElement("iFrame");
      newNode.setAttribute("id", iFrameDivID);
      newNode.setAttribute("src", "javascript:false;");
      newNode.setAttribute("scrolling", "no");
      newNode.setAttribute ("frameborder", "0");
    if (!pickerDiv)
      pickerDiv = document.getElementById(datePickerDivID);
    if (!iFrameDiv)
      iFrameDiv = document.getElementById(iFrameDivID);
    try {
      iFrameDiv.style.position = "absolute";
      iFrameDiv.style.width = pickerDiv.offsetWidth;
      iFrameDiv.style.height = pickerDiv.offsetHeight ;
      iFrameDiv.style.top = pickerDiv.style.top;
      iFrameDiv.style.left = pickerDiv.style.left;
      iFrameDiv.style.zIndex = pickerDiv.style.zIndex - 1;
      iFrameDiv.style.visibility = pickerDiv.style.visibility ;
      iFrameDiv.style.display = pickerDiv.style.display;
    } catch(e) {
  } catch (ee) {
Watch Question

Most Valuable Expert 2012
Top Expert 2008

1) You would need _doPostBack Javascript, and a unique control ID

2) I haven't done it specifically

3) Have you heard of AJAX?

4) .NET version?  2.0 or 1.1?

5) Why do you need a post-back?



hi Bob,
thank you for your reply.

i'm using ASP.net 2.0 with C# code behind and SQL Server 2000 Database.

The reason i need to do a post back is because the logic i need to implement i.e to add 15 working days to a current date (excluding weekends and bank holidays)  are held in a SQL Server Stored procedure.. so i need to implement a post back through my javascript code to invoke this stored procedure and return me a value that i need to populate back in a textbox

If you could give me examples of how to implement a post back through javascript that would be great.. and if you spare sometime and show me how i could implement this in my code posted above.. that would excellent..

Please help...
Most Valuable Expert 2012
Top Expert 2008
You need to find a way to get __doPostBack defined within your Javascript.  There is a way to get this by using ClientScript.GetPostBackEventReference.  Then you could call __doPostBack, which is what an event handler does:

Understanding the JavaScript __doPostBack Function


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