Keyboard Row LeetCode solution in JavaScript

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var findWords = function (words) {
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  const firstRow = {
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    q: true,
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    w: true,
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    e: true,
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    r: true,
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    t: true,
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    y: true,
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    u: true,
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    i: true,
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    o: true,
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    p: true,
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  };
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  const secondRow = {
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    a: true,
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    s: true,
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    d: true,
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    f: true,
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    g: true,
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    h: true,
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    j: true,
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    k: true,
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    l: true,
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  };
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  const thirdRow = {
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    z: true,
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    x: true,
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    c: true,
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    v: true,
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    b: true,
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    n: true,
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    m: true,
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  };
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  let result = [];
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  const helperFunc = (word) => {
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    let targetRow;
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    //Determine in which row the word should be;
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    if (firstRow[word[0].toLowerCase()]) targetRow = firstRow;
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    if (secondRow[word[0].toLowerCase()]) targetRow = secondRow;
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    if (thirdRow[word[0].toLowerCase()]) targetRow = thirdRow;
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    for (let i = 1; i < word.length; i++) {
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      if (!targetRow[word[i].toLowerCase()]) {
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        return false;
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      }
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    }
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    return true;
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  };
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  for (let i = 0; i < words.length; i++) {
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    if (helperFunc(words[i])) {
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      result.push(words[i]);
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    }
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  }
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  return result;
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};