#1002 - Find Common Characters

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Problem Description

Given a string array words, return an array of all characters that show up in all strings within the words (including duplicates). You may return the answer in any order.

Solution

/**
 * @param {string[]} words
 * @return {string[]}
 */
var commonChars = function(words) {
  return words
    .map(word => [...word])
    .reduce((common, word) => common.filter(s => {
      const index = word.indexOf(s);
      if (index !== -1) {
        word.splice(index, 1);
      }
      return index !== -1;
    }), [...words[0]]);
};