Sure, here's an example of a JavaScript function that accepts an array of letters and returns an array of words:

function lettersToWords(letters) {
  const letterMap = {
    'a': ['apple', 'ant', 'arrow'],
    'b': ['banana', 'ball', 'bird'],
    'c': ['cat', 'car', 'cup'],
    // Add more letters and corresponding words as needed
  };

  const words = [];

  letters.forEach(letter => {
    if (letterMap[letter]) {
      words.push(...letterMap[letter]);
    }
  });

  return words;
}

// Example usage
const letters = ['a', 'b', 'c'];
const words = lettersToWords(letters);
console.log(words); // Output: ['apple', 'ant', 'arrow', 'banana', 'ball', 'bird', 'cat', 'car', 'cup']

In this example, the function lettersToWords takes an array of letters as input and uses a predefined letterMap object to map each letter to an array of words. The function then iterates through the input letters, checks if they exist in the letterMap, and adds the corresponding words to the words array. Finally, it returns the array of words. You can customize the letterMap object to include more letters and their corresponding words as needed.