Удалить атрибут отключений JavaScript
document.getElementById('my-input-id').disabled = false;
Unsightly Unicorn
document.getElementById('my-input-id').disabled = false;document.getElementsByTagName("H1")[0].removeAttribute("class");// Makes the button disabled
document.getElementById("myButtonId").setAttribute("disabled", "");
// Removes disabled attribute
document.getElementById("myButtonId").removeAttribute("disabled");