Array of arrays

by mattography

JavaScript

var arr = ["L", "A", "T", "C", "H", "A", "C", "C", "E", "S", "S"],
  similarVals = a => a.reduce((p, c) => (p[p.length - 1][0] === void 0 ||
    p[p.length - 1][0] === c ? p[p.length - 1].push(c) : p.push([c]),
    p), [
    []
  ]);
console.log(JSON.stringify(similarVals(arr)));