Edit in JSFiddle

var ta = document.getElementById('ta');
var ip = document.getElementById('ip');
var ip1 = document.getElementById('ip1');

ta.value = '\n\n\n';

var count = function() {
    ip.value = ta.value.length;
    ip1.value = ta.maxLength || ta.maxlength;
};

ta.onkeyup = count;

count();

<textarea id="ta" maxlength="6"></textarea>
<br><br>
<lable>ta.value.length :</lable><input id="ip">
<br><br>
<lable>ta.maxLength :</lable><input id="ip1">

#ta{
    height: 150px;
    margin: 30px;
}