JavaScript: IE11 String.repeat() Prototype/Function

Still developing for IE11? Well, this prototype is used to repeat a string on IE11. It is used by padStart() and padEnd()

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 '';
		}
		// most browsers can not work with strings 1 << 28 chars or longer:
		if (str.length * count >= 1 << 28) {
			throw new RangeError('repeat count must not overflow maximum string size');
		}
		var maxCount = str.length * count;
		count = Math.floor(Math.log(count) / Math.log(2));
		while (count) {
			str += str;
			count--;
		}
		str += str.substring(0, maxCount - str.length);
		return str;
	}
}

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 '';
		}
		// most browsers can not work with strings 1 << 28 chars or longer:
		if (str.length * count >= 1 << 28) {
			throw new RangeError('repeat count must not overflow maximum string size');
		}
		var maxCount = str.length * count;
		count = Math.floor(Math.log(count) / Math.log(2));
		while (count) {
			str += str;
			count--;
		}
		str += str.substring(0, maxCount - str.length);
		return str;
	}
}
alert("123".repeat(10));

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