lpad javascript

1str.padStart(targetLength [, padString])

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

1var n = 123
2
3String("00000" + n).slice(-5); // returns 00123
4("00000" + n).slice(-5); // returns 00123
5("     " + n).slice(-5); // returns "  123" (with two spaces)