What this snippet does
Combining filter and map into one reduce avoids creating an intermediate array — useful when working with large datasets.
Expected output
[ 4, 16, 36, 64, 100 ] [ 4, 16, 36, 64, 100 ]
Why practise typing this
Typing functional patterns code builds muscle memory for the symbols and indentation JavaScript uses most, which prose-based typing tests never cover. DevType measures your words per minute and accuracy on this snippet and tracks the individual characters you mistype, so later lessons can target them.
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