title: Prevent text entry in textbox unless checkbox is checked
body: <p>I'm trying to prevent text from being entered in a textbox unless a checkbox that corresponds with the textbox is checked.</p>
  
  <pre><code>// Validate "Other" textbox
  var isOther = document.getElementById("isOther");
  isOther.addEventListener("input", function (evt) {
       // Checkbox must be checked before data can be entered into textbox
       if (isOther.checked) {
            document.getElementById("other").disabled = false;
       } else {
            document.getElementById("other").disabled = true;
       }
  });
  </code></pre>