The original question was edited. So the updated example answers:
To fill the same content:
Array(8).fill(1)
//=> [1, 1, 1, 1, 1, 1, 1, 1]
To fill sequential numbers, starting from 5:
Array(8).fill().map((element, index) => index + 5)
//=> [5, 6, 7, 8, 9, 10, 11, 12]
To fill sequencial characters, starting from ‘G’:
Array(8).fill().map((element, index) => String.fromCharCode('G'.charCodeAt(0) + index))
//=> ["G", "H", "I", "J", "K", "L", "M", "N"]