Resource Disposal: Haskell's Bracket pattern in JS

bracket.js

// http://cautionsingularityahead.blogspot.com/2012/07/resource-using-in-javascript.html

// Say you have a heavy-weight resource that you can explicitly finalize - either through
// some API or just by dropping a reference when you're done even if you want to hold onto
// the wrapper:
function Resource(a) {
  var res = "a resource of " + a;

  this.get = function() {
    return res;
  };

  this.dispose = function () {
    console.log('destroyed: ' + res);
    res = null;
  };
}

// A JS impl of Haskell's bracket pattern:
function bracket(before, during, after) {
  before();
  try {
    return during();
  } finally {
    after();
  }
}

// And an example of using bracket()
(function() {

  var res;
  bracket(
    function () { res = new Resource('foo'); },
    function () { console.log(res.get()); },
    function () { res.dispose(); res = null; }
  );

}());

// But it can be tailored more specifically to the resource disposal case...
function using(resource, user) {
  if (!resource || typeof resource.dispose !== 'function') {
    throw new Error('resource does not expose a dispose method');
  }
  try {
    user(resource);
  } finally {
    resource.dispose();
  }
}


// And you end up using it like C#:
(function() {

  using(new Resource('bar'), function (res) {
    console.log(res.get());
  });

}());