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Refactoring For jQuery

rfornal profile image bob.js Updated on ・1 min read

Set Up

Recently, in some client code, I found a lot of jQuery usage. While working with them to build a better test suite, I started with some simple refactoring to make these functions more testable.

The initial code looked like this ...

const testableCode1 = {
  test: function() {
    return testableCode.runTest();
  },
  runTest: function() {
    var elements = $('.elements');
    return elements.length;
  }
};
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Initial Test Coverage

There were no initial tests. Since we wanted to do some refactoring, we wound up with a simple pattern to allow for refactoring ...

describe('pre-refactor', function() {
  it('test before refactor', function() {
    var itemToReturn = $('<div></div>');
    spyOn(window, '$').and.callFake(function(item) {
      if (item === '.elements') {
        return itemToReturn;
      }
    });

    var result = testableCode1.test();

    expect(result).toEqual(1);
  });
});
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Refactor

Now, with these tests in place, we can refactor the code with a level of confidence that the functionality will remain the same.

Here's the refactored testableCode code ...

const testableCode2 = {
  test: function() {
    var elements = $('.elements');
    return testableCode2.runTest(elements);
  },
  runTest: function(items) {
    return items.length;
  }
};
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Rework Tests

Given this refactor, the old test put into place should still pass and we can now write tests without the spyOn being used ...

describe('post-refactor', function() {
  it('test before refactor', function() {
    var itemToReturn = $('<div></div>');
    spyOn(window, '$').and.callFake(function(item) {
      if (item === '.elements') {
        return itemToReturn;
      }
    });

    var result = testableCode2.test();

    expect(result).toEqual(1);
  });

  it('test after refactor', function() {
    var itemToReturn = $('<div>');
    var result = testableCode2.runTest(itemToReturn);
    expect(result).toEqual(1);    
  });
});
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Conclusion

Now that the code has been refactored, the initial test could easily be removed, making the tests much cleaner and simpler to work with.

Discussion (3)

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amersikira profile image
Amer Sikira

I can see that a lot of people are saying that jQuery is no go. But honestly, I still tend to use it where ever I can. Am I going to Hell? :D

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rfornal profile image
bob.js Author

Possibly ... I have heard the same conversations, but when I am prototyping, nothing's better.

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amersikira profile image
Amer Sikira

Yeah. I like it because it is easy to use, a lot of plugins, etc. There were some rumors that they' ll stop supporting and developing it, but as far as I know they did not.

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