实现两个超过正整数最大值的加和运算(js)

<script type="text/javascript">
	function add(a, b) {
		if(!a || !b) {
			throw Error('input invalid');
		}

		// state center
		let aString = a.trim();
		let bString = b.trim()
		let maxLength = getMaxLength(aString, bString);
		let temp = 0;
		let array = [];

		aString = aString.padStart(maxLength, '0');
		bString = bString.padStart(maxLength, '0');

		let aArray = aString.split('');
		let bArray = bString.split('');

		for(var i = maxLength-1; i >= 0; i-- ) {
			let count = toNumberAdd(aArray[i], bArray[i]);
			let tempResult = getSplit(count);
			let subTemp = Number(tempResult[1]) + Number(temp);

			if(subTemp >= 10){
				let subResult = getSplit(subTemp);

				array[i] = Number(tempResult[1]) + Number(temp) + Number(subResult[1]);
				temp = tempResult[0] + subResult[0];

			}else {
				array[i] = subTemp;
				temp = tempResult[0];	
			}
			
		}

		return temp == '1' ? temp + array.join('') : array.join('');
	}

	function getMaxLength(a, b) {
		let alength = a.trim().length;
		let blength =  b.trim().length;

		return Math.max(alength, blength);
	}

	function toNumberAdd(a,b) {
		return Number(a) + Number(b);
	}

	function getSplit(number) {
		let result = String(number/10);

		let a = result.split('.')[0];
		let b = result.split('.')[1] ? result.split('.')[1] : 0;

		return [a,b];
	}

	console.log('result is : ', add('11', '89'));
</script>