Answer 1

function input(num) {
	const strNum = String(num)
    
	if (strNum.length === 1) return strNum

	const d = Math.pow(10, strNum.length - 1)
	const res = Math.floor(num / d)
	const left = num % d
    
    console.log('res', res)
    console.log('d', d)
	return input(left) + res + ''
}

console.log(input(1234)) // '4321'

Answer 2

留下了没技术的泪水