JSFiddle - React, Tailwind, and code Playground

HTML

<input id="textbox" type="text" readonly />
<div id="message"></div>

JavaScript

var message = document.getElementById('message');
var textbox = document.getElementById('textbox');

textbox.onkeypress = function(e) {
	var key = e.keyCode;
    
    if (key === 13) { // Enter
        textbox.readOnly = true;
        message.textContent = 'Enter!';
    } else {
    	message.textContent = '';
    }
};