1const str1 = '5';
2
3console.log(str1.padStart(2, '0'));
4// expected output: "05"
5
6const fullNumber = '2034399002125581';
7const last4Digits = fullNumber.slice(-4);
8const maskedNumber = last4Digits.padStart(fullNumber.length, '*');
9
10console.log(maskedNumber);
11// expected output: "************5581"
12

1export function padStart(number, digits = 2, emptyDigit = 0) {
2	let length = 0;
3	let n = Math.abs(number);
4	let absoluteNumber = n;
5	do {
6		n /= 10;
7		length++;
8	} while (n >= 1);
9	const prefix = Array(Math.max((digits - length) + 1, 0)).join(emptyDigit);
10	return number < 0 ? `-${prefix}${absoluteNumber}` : prefix + number;
11}
12
13export default padStart;
14