London | 26-ITP-Jan | Angela McLeary | Sprint 1 | Sprint 1

[AngelaMcLeary]

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Changelist

This PR is about fixing median.js, Implementing dedupe.js, max.js, sum.js and refactoring include.js.

[cjyuan]

This test should fail if the function returns the original array (instead of a copy of the original array).

The current test checks only if both the original array and the returned array contain identical elements.
In order to validate the returned array is a different array, we need an additional check.

Can you find out what this additional check is?

[AngelaMcLeary]

Hi @cjyuan, Thank you for the feedback. I added an additional assertion to ensure the dedupe function returns a new array instance, not the original array. The previous test only checked for value equality using .toEqual(), which would still pass even if the function simply returned the input array.To properly validate the acceptance criteria, the test is now fortified.

[cjyuan]

When a string representing a valid numeric literal (for example, "300") is compared to a number,
JavaScript first converts the string into its numeric equivalent before performing the comparison.
As a result, the expression 20 < "300" evaluates to true.

To test if the function can correctly ignore non-numeric values,
consider including a string such as "300" in the relevant test cases.

[AngelaMcLeary]

Hi @cjyuan, Thank you for your feedback. I have updated the test to include an edge case for numerical string.

[cjyuan]

Decimal numbers in most programming languages (including JS) are internally represented in "floating point number" format. Floating point arithmetic is not exact. For example, the result of 46.5678 - 46 === 0.5678 is false because 46.5678 - 46 only yield a value that is very close to 0.5678. Even changing the order in which the program add/subtract numbers can yield different values.

So the following could happen

  expect( 1.2 + 0.6 + 0.005 ).toEqual( 1.805 );                // This fail
  expect( 1.2 + 0.6 + 0.005 ).toEqual( 1.8049999999999997 );   // This pass
  expect( 0.005 + 0.6 + 1.2 ).toEqual( 1.8049999999999997 );   // This fail

  console.log(1.2 + 0.6 + 0.005 == 1.805);  // false
  console.log(1.2 + 0.6 + 0.005 == 0.005 + 0.6 + 1.2); // false

Can you find a more appropriate way to test a value (that involves decimal number calculations) for equality?

Suggestion: Look up

• Checking equality in floating point arithmetic in JavaScript
• Checking equality in floating point arithmetic with Jest

[AngelaMcLeary]

Hi @cjyuan, Thank you for your feedback. I understand now why decimal values need special handling. toBeCloseTo() is a better choice because it checks that the result is close enough within a small margin, which avoids issues caused by floating‑point rounding.