const numStr = "123456";
const numArr = strNum.split('').map((item) => parseInt(item, 10))
//OUTPUT
[1, 2, 3, 4, 5, 6]
// === STEP BY STEP ===
const step1 = numStr.split('')
// -> ['1', '2', '3', '4', '5', '6']
const step2 = step1.map((item) => parseInt(item))
// -> [1, 2, 3, 4, 5, 6]