Textarea limit IME

HTML

<textarea id="noime" readonly></textarea>

CSS

#noime{
  width:500px;
  height:300px;
}

JavaScript

document.querySelector('#noime').addEventListener('keydown',(e)=>{
let textbox=document.querySelector('#noime')
let character;
if (e.Code=="Backspace"){
console.log('backspace');
textbox.value=textbox.value.substr(0,textbox.value.length-1)
return;
}
if (e.getModifierState('CapsLock')) {
	character=String.fromCharCode(e.keyCode).toUpperCase();
}else{
	character=String.fromCharCode(e.keyCode).toLowerCase();
}
textbox.value+=character;
})