Solution to Diaz's brainteaser
public javascript v1 · immutablearr.join(' ').replace(/([a-z]) \1((?: \1)+)/g, '$1 $1 <span>$2</span>').replace(/<span> /g, '<span>')arr.join(' ').replace(/([a-z]) \1((?: \1)+)/g, '$1 $1 <span>$2</span>').replace(/<span> /g, '<span>')