Simplify/optimize map-reduce in useLoadData

[baker-ling]

Proposed changes

I saw the usage of map-reduce in useLoadData, and I think that those can be simplified by using Array.prototype.every and Array.prototype.some instead.

In addition to the simplification, this should provide some time and space optimization.

• Time: .some() and .every() will terminate early (still O(n) though)
• Space: should also be reduced from O(n) to O(1) because they do not build a new array like .map() does

Fixes #41

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[nthurow]

It looks good to me! Do the tests work locally? Looks like we don't have those running as a PR check yet...