Javascript for character count on keypress

Javascript for character count on keypress 

<script language="javascript" type="text/javascript">
maxL = 1000;
    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>

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It is used like as mention below

 <asp:TextBox ID="txtImportaintInfo" runat="server" TextMode="MultiLine"
                                    CssClass="textarea_field2"  onpaste="return false" onkeypress="return taLimit(this)" onkeyup="return taCount(this,'myCounter1')"></asp:TextBox>
                                 
<br />     You have <b><span id="myCounter1">1000</span></b>
                                characters remaining for your description...</td>