_.eq redundant comparison when both null

[ahonn]

in _.eq function:

 eq = function(a, b, aStack, bStack) {
    // Identical objects are equal. `0 === -0`, but they aren't identical.
    // See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
    if (a === b) return a !== 0 || 1 / a === 1 / b;
    // A strict comparison is necessary because `null == undefined`.
    if (a == null || b == null) return a === b;
   ......
}

a === b is true when a = null and b = null, so the function will return true.
and then, if (a == null || b == null) is true, return a === b.
It would never be true, why not directly return false:

if (a == null || b == null) return false;

I checked the #2180 and #2179 , but I still don't understand why not directly return false?

[jridgewell]

Yah, looks like we could. Want to open a PR?

[ahonn]

Nice, I have opened a PR #2630

[bnjmnt4n]

@ahonn since we are using a == null || b == null, a and b could be null or undefined due to == not being a strict equal comparison. Hence a === b is needed to ensure that a and b are not regarded as the same, if one is null and the other is undefined.

[jridgewell]

Yes, but we've already done a a === b check above it. So, if either a or b is null or undefined, we know that both aren't.

[bnjmnt4n]

Yes, but we've already done a a === b check above it

Ah, I completely missed that :| Thanks @jridgewell!

[ahonn]

When running if (a == null || b == null) ..., a === b would never be true.
Because if a === b is true, will return a !== 0 || 1 / a === 1 / b. So, That must be false.