Uncaught TypeError: Cannot call method 'toLowerCase' of undefined

Question

I ran into a very vague error while doing some simple jQuery DOM manipulation.

The line that triggered the error is the following:

$(this).closest(\'tr\')

Answer 1

I don't know what you expect the value of this to be in your "success" handler, but I bet it's not what you think. Save this outside the "$.ajax()" call:

var clicked = this;
$.ajax(
  // ...
  success: function(res) {
    if (res) {
      $(clicked).closest('tr').remove();
    }
    else {
      // ...
    }
  }
);