function like IsObject()

[BillLumbergh]

Is there a Javascript function that simply checks to see if what I am referring to is an object on a web form? For example, the Javascript would be doing some client side validation of a web form that may or may not contain a checkbox. If the checkbox exists, I want to run some validation on it. What I am essentially looking for is a Javascript function that will do this:

if (IsObject(document.form.chkMyCheckbox))
{
// means for field exists
do this;
}
else
{
form field does not exist, do nothing
}

What is the means of performing the IsObject() call? I'm guessing this is pretty basic; I just don't know it. The search I ran did not find anything that looked too promising.

Thanks.

 

[kaht]

if (document.form.chkMyCheckbox) should be sufficient.

Here's an example, try it first with the <!-- --> comments and then again without them.

<script language=javascript>

function checkForCheckbox() {
   alert((blahForm.blahCheckbox) ? "Checkbox exists" : "Checkbox does not exist")
}

</script>
<form name=blahForm>
<input type=button value='check for checkbox' onclick='checkForCheckbox()'><br>
<!-- <input type=checkbox name=blahCheckbox> -->
</form>

-kaht

 

[adam0101]

Dang, kaht beat me. Well if you wanted to use an IsObject function, this should do:

function IsObject(obj){
  return obj ? true : false;
}

Adam
while(ignorance){perpetuate(violence,fear,hatred);life=life-1};

 

[kaht]

Adam, is it just me, or once you get used to using the "?" operator do you hardly ever use if statements anymore?

-kaht

 

[adam0101]

It's a nice little shortcut, but I still use if(condition){action} statements if there's no "else" or if I need to nest multiple "if" statements for readability.

Adam
while(ignorance){perpetuate(violence,fear,hatred);life=life-1};

 

[BillyRayPreachersSon]

I think you're right there, kaht. Once you know the syntax of these things (for example, the order of the 4 directional elements used in CSS positioning - top, right, bottom, left - N,E,S,W), you use them more and more.

With regards to the ternary operator (? it certainly saves a few bytes, and in some cases makes code look a whole lot neater and more compact.

It also comes in handy when entering 20-line JavaScript competitions (shameless plug for my 3rd-place entry:

http://www.soterm.com/dan/princess.html

;o)

Dan

 

[adam0101]

Dan,
Nice game for 20 lines of code, but I got to level 28 before I got bored. I only had to move left, then up for every level.

Adam
while(ignorance){perpetuate(violence,fear,hatred);life=life-1};