Count the Number of Consistent Strings LeetCode solution in JavaScript

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/**
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 * @param {string} allowed
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 * @param {string[]} words
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 * @return {number}
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 */
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var countConsistentStrings = function (allowed, words) {
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  const hashmap = new Map();
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  let output = 0;
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  for (let i = 0; i < allowed.length; i++) {
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    hashmap.set(allowed[i], 1);
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  }
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  for (let i = 0; i < words.length; i++) {
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    const word = words[i];
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    output++;
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    for (let j = 0; j < word.length; j++) {
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      if (!hashmap.has(word[j])) {
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        output--;
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        break;
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      }
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    }
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  }
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  return output;
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};