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Wrong value for _.isEqual(0, new Number(Number.MIN_VALUE)) #2815

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Wrong value for _.isEqual(0, new Number(Number.MIN_VALUE)) #2815

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Wrong value for _.isEqual(0, new Number(Number.MIN_VALUE))
dubzzz Oct 30, 2019
b305986
Update test/objects.js
dubzzz Apr 10, 2020
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2 changes: 2 additions & 0 deletions test/objects.js
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Expand Up @@ -330,6 +330,8 @@
assert.ok(!_.isEqual(-0, 0), 'Commutative equality is implemented for `0` and `-0`');
assert.ok(!_.isEqual(null, void 0), '`null` is not equal to `undefined`');
assert.ok(!_.isEqual(void 0, null), 'Commutative equality is implemented for `null` and `undefined`');
assert.ok(!_.isEqual(0, new Number(Number.MIN_VALUE)), '`0` is not equal to `new Number(Number.MIN_VALUE)`');
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assert.ok(!_.isEqual(new Number(Number.MIN_VALUE), 0), '`new Number(Number.MIN_VALUE)` is not equal to `0`');

// String object and primitive comparisons.
assert.ok(_.isEqual('Curly', 'Curly'), 'Identical string primitives are equal');
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2 changes: 1 addition & 1 deletion underscore.js
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Expand Up @@ -1223,7 +1223,7 @@
// Object(NaN) is equivalent to NaN.
if (+a !== +a) return +b !== +b;
// An `egal` comparison is performed for other numeric values.
return +a === 0 ? 1 / +a === 1 / b : +a === +b;
return +a === 0 && +b === 0 ? 1 / +a === 1 / b : +a === +b;
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@jgonggrijp jgonggrijp Apr 7, 2020 •
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This just collapses the entire expression to +a === +b, since to enter the first branch, both +a and +b must already have been found to exactly equal 0. You can preserve the original fuzziness and still make the comparison symmetric by using a disjunction instead of a conjunction:

Suggested change
return +a === 0 && +b === 0 ? 1 / +a === 1 / b : +a === +b;
return +a === 0 || +b === 0 ? 1 / +a === 1 / +b : +a === +b;

It may actually be worth considering to also allow fuzziness when both values are close to zero but neither is exactly zero. This seems more consistent as it doesn't treat zero as a special case:

Suggested change
return +a === 0 && +b === 0 ? 1 / +a === 1 / b : +a === +b;
return +a === +b || 1 / +a === 1 / +b;

However, maybe there is something to say for making the comparison symmetrically exact instead of symmetrically fuzzy:

Suggested change
return +a === 0 && +b === 0 ? 1 / +a === 1 / b : +a === +b;
return +a === +b;

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@dubzzz dubzzz Apr 10, 2020 •
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Actually this is not fully equivalent. The initial check distinguishes 0 from -0 which was already the case before my change. It is not the case of the suggested change:

---        return +a === 0 && +b === 0 ? 1 / +a === 1 / b : +a === +b;
+++        return +a === +b;

As in JavaScript -0 === 0 🤔
Alternatively we can use: Object.is(+a, +b)

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Good point. So actually we have four symmetric options, from most to least fuzzy:

(1) +0 === -0 and values that approach zero from the same side are equivalent.

+a === +b || 1 / +a === 1 / +b

(2) +0 !== -0 and values that approach zero from the same side are equivalent.

+a === 0 || +b === 0 ? 1 / +a === 1 / +b : +a === +b

(3) +0 === -0, otherwise exact comparison.

+a === +b

(4) +0 !== -0, entirely like Object.is but compatible with IE.

+a === 0 && +b === 0 ? 1 / +a === 1 / +b : +a === +b

case '[object Date]':
case '[object Boolean]':
// Coerce dates and booleans to numeric primitive values. Dates are compared by their
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