About JavaScript function parameters

Question

I'm newer in JavaScript.So maybe my question will seem naive.

My JavaScript Code:

<script type = "text/javascript">
 var defaultText = "Enter your text here";
 function WaterMark(txt, evt) 
 {
    if(txt.value.length == 0 && evt.type == "blur")
    {
        txt.style.color = "gray";
        txt.value = defaultText;
    }
    if(txt.value == defaultText && evt.type == "focus") 
    {
        txt.style.color = "black";
        txt.value=""; 
    }
 }

ASP declaration:

<asp:TextBox ID="TextBox1" runat="server" Text = "Enter your text here
ForeColor = "Gray" 
onblur = "WaterMark(this, event);" 
onfocus = "WaterMark(this, event);">

My quetstion is about parameters of this two events:

  onblur = "WaterMark(this, event);" 
  onfocus = "WaterMark(this, event);"

If i understood correctly word this means the current control.

And what is meaning of the second parameter, event ?

Thank you in advance!

msigman · Accepted Answer · 2012-03-31 22:02:05Z

1

Those are the event arguments, or EventArgs. They can contain a set of variables that existed at the time the event was created, to provide additional context to the event handler. It's basically a way to pass information into your event handler.

http://pietschsoft.com/post/2008/11/07/ASPNET-AJAX-Create-a-JavaScript-Component-with-Events.aspx

edited Mar 31, 2012 at 22:02

answered Mar 31, 2012 at 21:51

msigman

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Aravindan R · Accepted Answer · 2012-03-31 21:56:45Z

1

Its the event object which contains information about the currently fired event. In IE, the event object is in the global "window" object. Mozilla/Chrome pass it as a parameter to the event handler

In the first line of your event handler, you can do this to support all browsers

event = event || window.event

If the "event" parameter is not present take it up from the window object. It will not be present in IE.

answered Mar 31, 2012 at 21:56

Aravindan R

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