JavaScript validation function on Firefox

Question

I have the following code which works perfect in IE for a textarea element.

<textarea name="mem_message" cols="25" rows="5"
  onkeypress="return taLimit(this)" 
  onkeyup="return taCount(this,'myCounter')">
    <? echo $_SESSION['mem_message']; ?>
</textarea>

It calls a validation function:

<script language="Javascript"><!--Counter for Message Box -->

maxL=100;
var bName = navigator.appName;
function taLimit(taObj) {
    if (taObj.value.length==maxL) return false;
    return true;
}

function taCount(taObj,Cnt) { 
    objCnt=createObject(Cnt);
    objVal=taObj.value;
    if (objVal.length>maxL) objVal=objVal.substring(0,maxL);
    if (objCnt) {
        if(bName == "Netscape"){    
            objCnt.textContent=maxL-objVal.length;}
        else{objCnt.innerText=maxL-objVal.length;}
    }
    return true;
}
function createObject(objId) {
    if (document.getElementById) return document.getElementById(objId);
    else if (document.layers) return eval("document." + objId);
    else if (document.all) return eval("document.all." + objId);
    else return eval("document." + objId);
}
</script>

All the above works on IE only. On Firefox it won't even focus on the box.

Answer 1

Few pointers:

• Don't use language="javascript", it's deprecated.
• Don't use eval for property access, it's slow and unnecessary.
• Don't sniff for "Netscape", instead check property/method existence/compliance (innerText/textContent)
• Don't name a method for receiving an element as "createObject", it's misleading.
• Don't perform undeclared assignment (maxL = 100), it's error prone.
• Don't capitalize variable names that are not constructors (or namespaces), for convention.
• Try not to declare functions in global scope, to avoid name conflicts.

Answer 2

Here's a better script to count characters in a textarea: http://sliceofcake.wordpress.com/2007/08/16/count-characters-in-a-textarea/

Hope it's what you're looking for!

Answer 3

The attributes for event handlers are meant to be in all lower case; have you tried onkeyup rather than onKeyUp, etc.?

Answer 4

Please read Unobtrusive JavaScript here http://en.wikipedia.org/wiki/Unobtrusive_JavaScript before doing any development in JavaScript.

You will thank me many times over later!