What this snippet does
tap injects logging or debugging into a pipeline without mutating the value or breaking the chain.
Expected output
input: 1 ... input: 5 output: 2 ... output: 10 [ 6, 8, 10 ]
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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