polyfill.js

// String.prototype.padStart
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart
if (!String.prototype.padStart) {
	String.prototype.padStart = function padStart(targetLength, padString) {
		targetLength = targetLength >> 0; //truncate if number, or convert non-number to 0;
		padString = String(typeof padString !== 'undefined' ? padString : ' ');
		if (this.length >= targetLength) {
			return String(this);
		} else {
			targetLength = targetLength - this.length;
			if (targetLength > padString.length) {
				padString += padString.repeat(targetLength / padString.length); //append to original to ensure we are longer than needed
			}
			return padString.slice(0, targetLength) + String(this);
		}
	};
}

// String.prototype.repeat
// https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
if (!String.prototype.repeat) {
	String.prototype.repeat = function(count) {
		'use strict';
		if (this == null) {
			throw new TypeError('can\'t convert ' + this + ' to object');
		}
		var str = '' + this;
		count = +count;
		if (count !== count) {
			count = 0;
		}
		if (count < 0) {
			throw new RangeError('repeat count must be non-negative');
		}
		if (count === Infinity) {
			throw new RangeError('repeat count must be less than infinity');
		}
		count = Math.floor(count);
		if (str.length === 0 || count === 0) {
			return '';
		}
		// Ensuring count is a 31-bit integer allows us to heavily optimize the
		// main part. But anyway, most current (August 2014) browsers can't handle
		// strings 1 << 28 chars or longer, so:
		if (str.length * count >= 1 << 28) {
			throw new RangeError('repeat count must not overflow maximum string size');
		}
		var rpt = '';
		for (var i = 0; i < count; i++) {
			rpt += str;
		}
		return rpt;
	}
}