Set basics in JavaScript

What this snippet does

Set automatically deduplicates — adding a value that already exists is silently ignored.

Expected output

3
[ 1, 2, 3 ]
false
true

Why practise typing this

Typing set 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.

More JavaScript practice

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