beforeEach Scope in Jasmine Unit Tests

Understanding the scope of beforeEach() in Jasmine describe() blocks.

describe('Testing the scope of beforeEach()', function() {
  var myGlobalVar,
      couldBeTrouble = false;

  beforeEach(function() {
    myGlobalVar = {
      a: 'Alpha',
      b: 'Beta',
      g: 'Gamma'
    };
  });

  it('maps the g key to the word Gamma', function() {
    expect(myGlobalVar.g).toEqual('Gamma');
  });

  describe('overwriting g in beforeEach', function() {
    beforeEach(function() {
      myGlobalVar.g = 'Not Gamma!';
      myGlobalVar.d = 'Delta';
      couldBeTrouble = true;
    });

    it('now maps the g key to the prhase \'Not Gamma!\'', function() {
      expect(myGlobalVar.g).toEqual('Not Gamma!');
    });
  });

  describe('using a another describe block', function() {
    it('once more maps the g key back to the word Gamma', function() {
      expect(myGlobalVar.g).toEqual('Gamma');
      expect(myGlobalVar.d).not.toBeDefined();
    });
  });

  it('set the value of couldBeTrouble earliers, but we didn\'t clean it up', function() {
    expect(couldBeTrouble).toBe(true);
  });
});