function countMostFrequentLetters(string)

const letterCounts = {};

for (const char of string)

// check if char is alphabet

if (char.toLowerCase() !== char.

)

const lowerChar = char.toLowerCase();

letterCounts[lowerChar] += letterCounts[lowerChar] ?

: 0;

}

}

const maxCount = Math.max(...Object.values(letterCounts));

// print most popular letters

const mostPopularLetters = [];

for (const [key, value] of Object.

(letterCounts))

if (value === maxCount)

mostPopularLetters.push(

);

}

}

return mostPopularLetters;

}

console.log(countMostFrequentLetters('mango and oranges')); // ['a', 'n']