How do I find the pixel equivalent of an "em?"

[programmer-in-training]

How do I find the pixel equivalent of an "em?"

[Ingolme]

There really isn't a way. The "em" is set by the default font size of the user's browser. If you want pixel values just use px as a unit instead.Though...Maybe with javascript you can detect it, something like this:

<div style="height: 1em" id="check"></div><script type="text/javascript">  var emSize = document.getElementById("check").offsetHeight;  // Use the variable "emSize" wherever you need the pixel value of the em unit</script>

[programmer-in-training]

That works. I prefer to have "visibility: hidden" and var emSize = check.offsetHeight; do I really need all that document.getElementById() confusion?Also, how do I find the height of the <td> I'm in? (I'm trying to subtract 1 em from 100% height.)

[programmer-in-training]

EDIT: That was a nice function to find the em size, but I realized I actually don't need it! Instead of "100%" I put in "menu.offsetHeight" and now it works. Thanks though it will be very useful. I've had to use less efficient workarounds before I came to these forums! Wonder why I never noticed them at w3schools before.... :)Also, I see why document.getElementById() would be useful if you're searching for a string.

[Synook]

Using the element's ID directly as an object without an assignment is not really correct, and isn't part of the W3C standard. Always use document.getElementById().

menu.offsetHeight; //Incorrect (though will work)menu = document.getElementById("menu"); //Correctmenu.offsetHeight; //Now also correct because of the assignment on the line above

By the way, an "em" is the width of the letter m at the current font size.

[jeffman]

My version of a little routine that saves a lot of typing:

function gg(id) {   return document.getElementById(id);}//call it like this:gg("id");

A lot of people use a $ instead of gg, but that makes my perl/php confusing. I remember "gg" by thinking of it as "go get."

[Ingolme]

"$" is a valid function name in Javascript?

[jesh]

No, but it is in jQuery - which seems to be fairly popular.http://jquery.com/

[jeffman]

Actually, it is. C/P this to be sure.

function $(){   alert ("Hello");}$();

I'm surprised you haven't seen this. It's in dozens of "My top-ten Javascript tips" pages around the net. I suppose it could stop being legal without warning; I don't really know. And as I said, I don't use it.

[justsomeguy]

Yeah, like DD said there are quite a few libraries that define the $ function to replace document.getElementById. It confused the crap out of me until I realized that $ was a legal function name, I was assuming it was some operator where everyone but me got the memo.

function $(s){  return document.getElementById(s);}val = $('elId').value;$('elId').style.display = 'none';

It just makes the code a little cleaner, it looks more like you're working directly with the object instead of working with document.getElementById.

[jesh]

Actually, it is.

Ahh, right. I knew it was a valid function name. I had assumed that the OP was asking if "$" was a built in feature of javascript/DOM like "alert", "getElementById", etc.