That closure vs bind

Created by: pinoniq

Is there a specific reason why the JS code of bootstrap is riddled with closures?

var that = this;

For instance the modal:

  var that = this;
  this.backdrop(function () {
      var transition = $.support.transition && that.$element.hasClass('fade')

      if (!that.$element.parent().length) {
        that.$element.appendTo(that.$body) // don't move modals dom position
      }

      ...
  }

...

  Modal.prototype.backdrop = function (callback) {
    ...
        callback()
  }

We are passing a callback to a method of the same object. We could remove the var that = this; and call the callable using:

callback.apply(this);

Maybe this could/should all be cleaned up.