To enable a
button
when text is entered, do this: input.addEventListener('change', e => button.disabled = e.target.value === '')
So if this is your input and a button:
<input id="my-input">
<button id="my-button" disabled>Click Me</button>
Then you can enable/disable the button based on whether something is in the input with this JavaScript:
document.getElementById("my-input").addEventListener('input', e => {
document.getElementById("my-button").disabled = e.target.value === '';
});