how could i change the value, named bytecnt - extjs4

Question

items: [{
rowspan:3,
columnWidth: 0.5,
margin: '10 10 10 10',
xtype: 'fieldset',
title:'SMS',
enableKeyEvents: true,
items: [{
xtype:'textarea',
width: 200,
height: 160,
id: 'content',
value: '',
enableKeyEvents: true,
listeners: {
keyup: function(form, e) {
var cnt2;
var len2;
var han2;
var varCont;
len2 = 0;
han2 = 0;
varCont = this.value;
for( cnt2 = 0 ; cnt2 < varCont.length; cnt2++ ){
if( varCont.charCodeAt(cnt2) > 255 ){
len2 += 2;
han2 += 2;
}else{
len2 ++;
}
}
Ext.getCmp('bytecnt').setValue(len2); //here is problem
}//keyup
}//listener
},{
xtype:'text',
html:"<input id='bytecnt' name='bytecnt' width='20' value='1'>",
width: 200,
height:20
}]

Answer 1

Ext.getCmp() is for looking up components by ID. Since your input field is not a component (but rather, the HTML of a component), but just an HTML element, you could use Ext.get() to retrieve it. But remember, since the input field you're retrieving with Ext.get() isn't a component, setValue() also won't work.
Why, though, are you using xtype: text with an HTML configuration of an text input field? Why not just use xtype: 'textfield' and allow Ext JS to manage that stuff for you? You can still configure everything else you need on it, but then be able to interact with it as a component.