how to call a javascript function and pass a field from javascript

depending on the event type you want, onclick, onsubmit, onblur etc
I'll use on click it easy
<script language="javascript">
function sendData(myData) {
   if (myData == 99) {
       alert("Here I Am");
   }
}
</script>

<input type="text" name="txt" id="txt" size="25" />
<input type="button" value="Go" onclick="sendData(document.getElementById('txt').value);"

<script>
function checkFrm()
{
var x= document.getElementById('txDt1').value;
      if(x == "" || x == 99)
      {
            return true;
      }
      else
      {
           
            return false;
      }
}
</script>

<form action="http://www.sembel.net/tools/q.php" onsubmit="return checkFrm(this)">
      <input type=text name="txDt1" value="11">
      <input type=submit>
</form>

Thanks for all of the replies.  I'm still a little lost.  
I'm actually calling this from a javascript function.  So I don't have the events like onsubmit= etc...
The form doesn't have a name, just an id...


Russell

I tried this: check_date(document.forms['Form1'].txDt1)
substituting Form1 above because it's the id, but I still get 'Error on page'

you have to do something to call the script.
They aren't just called magically.

When do you want the script called?
What do you want to happen when the script is called.
Decide that, post code, then we can help, other wise we are just guessing as to how you want to handle this.

The code below gives me an error on page.  Save2() is called when a button is clicked.
The form has a field txDt1
When a button is clicked, save2() is called and the code below executes.  Inside the code below there's a call to another function, check_date() and I just need to pass a field object to the function because within the checkdate function, it's doing a getelementbyid(fld).value to get the value in the field

function Save2(){
      var a=document.getElementById("txDt1").value
      var b=document.getElementById("txDt2").value
      var c=document.getElementById("txtPrName").value      
      var d=document.getElementById("cbQCSpecialist").options.selectedIndex
      var e=document.getElementById("cboAuditor").options.selectedIndex
      var pct=document.getElementById("txPrc2").value      
      
      a=Trim(a)
      b=Trim(b)
      c=Trim(c)
      pct = Trim(pct)
      
      if (a == 0){
            alert("You must first enter a valid start date.")
            return false
      }
      
      if (b == 0){
            alert("You must first enter a valid end date.")
            return false
      }
      
      if (c == 0){
            alert("You must first enter a Project Name.")
            return false
      }
      if (d < 1){
            alert("You must first select a resource for this project.")
            return false
      }
      if (e < 1){
            alert("You must first select an Manager for this project.")
            return false
      }

      if (pct == 0){
            alert("You must first enter a valid amount.")
            return false
      }
      
      ii=document.getElementById("cboTmpQuestion").options.selectedIndex
      if (ii < 0){
            alert("You must first select a Question for this project.")
            return false
      }
      
      if check_date(document.forms['Form1'].txDt1) == 99 {
            alert("You must first enter a valid date!")
            return false
      }

      return false

      
}

If as you said "it's doing a getelementbyid(fld).value to get the value in the field" why you needs to pass the field into the check_date?

I think the primary error of your page is you missing the parentheses around your if condition:
<code>
      if (check_date(document.forms['Form1'].txDt1) == 99) {
            alert("You must first enter a valid date!")
            return false
      }
</code>

If in the check_date already has the document.getElementById(fld).value, please try:
<code>
      if (check_date("txDt1") == 99) {
            alert("You must first enter a valid date!")
            return false
      }
</code>

A best pratice for Javascript is place a semicolon after every statement, in case you want to compress your code later, it will be a great help

post the rest of the code, like the form,

from what I see, document.forms['Form1'].txDt1 should be this document.forms['Form1'].txDt1.value,

but this is an old way of doing it, you should be doing it to W3C way of document.getElemenetById("txtDt1").value
assuming that you added the ID attribute in that form field.