Codigo:
<html>Esta basado en este codigo que encontré, que hacia exactamente lo que necesito, pero con caracteres: podesi ver el original aquí:
<head>
<title>funcion contar caracteres con javascript</title>
<script type="text/javascript">
<!-- Original: Ronnie T. Moore -->
<!-- Begin
function textCounter(field, countfield, maxlimit) {
if (field.value.length > maxlimit) // if too long...trim it!
field.value = field.value.substring(0, maxlimit);
// otherwise, update 'characters left' counter
else
countfield.value = maxlimit - field.value.length;
}
// End -->
</script>
</head>
<body>
<!-- textCounter() parameters are: text field, the count field, max length -->
<form name="myform" action="YOUR-SCRIPT.CGI">
<font size="1" face="arial, helvetica, sans-serif"><p>( El límite es de 125 caracteres. )<br>
<textarea name="message" wrap="physical" cols="28" rows="4"
onKeyDown="textCounter(this.form.message,this.form.remLen,125);"
onKeyUp="textCounter(this.form.message,this.form.remLen,125);"></textarea> <br>
<input readonly type="text" name="remLen" size="3" maxlength="3" value="125"> caracteres</font> </p>
</form>
</body>
</html>
http://www.gamarod.com.ar/javascript/99-funcion-contar-caracteres-con-javascript.htm
y el codigo (por aquello de las páginas muertas):
<html>
<head>
<title>funcion contar caracteres con javascript</title>
<script type="text/javascript">
<!-- Original: Ronnie T. Moore -->
<!-- Begin
function textCounter(field, countfield, maxlimit) {
if (field.value.length > maxlimit) // if too long...trim it!
field.value = field.value.substring(0, maxlimit);
// otherwise, update 'characters left' counter
else
countfield.value = maxlimit - field.value.length;
}
// End -->
</script>
</head>
<body>
<!-- textCounter() parameters are: text field, the count field, max length -->
<form name="myform" action="YOUR-SCRIPT.CGI">
<font size="1" face="arial, helvetica, sans-serif"><p>( El límite es de 125 caracteres. )<br>
<textarea name="message" wrap="physical" cols="28" rows="4"
onKeyDown="textCounter(this.form.message,this.form.remLen,125);"
onKeyUp="textCounter(this.form.message,this.form.remLen,125);"></textarea> <br>
<input readonly type="text" name="remLen" size="3" maxlength="3" value="125"> caracteres</font> </p>
</form>
</body>
</html>
