JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id = 'textField'> <br>
Event oninput: <span id="result"></span> <br>
<input type="button" id = 'buttonField' value="Кнопка" disabled ="disabled" ><br>

JavaScript

var inputText = document.getElementById('textField');
var inputButton = document.getElementById('buttonField')

inputText.oninput = disableButton;

function disableButton() {
    document.getElementById('result').innerHTML = inputText.value;
    if(inputText.value != ''){
    	inputButton.disabled = false;
    }else{
    	inputButton.disabled = true;
    }
}