<input class="form__input" type="checkbox">
<button disabled id="form__button">кляк</button>
$(".form__input").click(function() {
  if (($(this).prop("checked"))) {
    $("#form__button").removeAttr("disabled");
  } else {
    $("#form__button").attr("disabled", "disabled");
  }
})

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.min.js