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export default function getRandom(digit) {
	window._CASH_RANDOM ? '' : window._CASH_RANDOM = {};
	var _cash_random = window._CASH_RANDOM || {},
		_digit = digit || 4,
		_random = getRandomSimple();

	while (_cash_random[_random]) {
		_random = getRandomSimple();
		if (!_cash_random[_random]) break;
	}

	window._CASH_RANDOM[_random] = _random;

	return _random;

	//随即返回随机数  --  可能重复
	function getRandomSimple() {
		var random = '';
		for (var i = 0; i < _digit; i++) {
			var r = Math.floor(Math.random() * 10);
			random += r.toString();
		}
		return random.toString();
	}
}