after.js

describe('A test', function() {
  set('data', function() {
    return { some: 'stuff' };
  });

  set('subject', function() {
    return new FooThing(data);
  });

  it('does stuff', function() {
    expect(subject.method()).toBe('whatever');
  });
});

before.js

describe('A test', function() {
  var subject;
  var data;

  beforeEach(function() {
    data = {
      some: 'stuff'
    };

    subject = new FooThing(data);
  });

  afterEach(function() {
    data = null;
    subject = null;
  });

  it('does stuff', function() {
    expect(subject.method()).toBe('whatever');
  });
});