js大整数相加函数(支持超过16位的高精度number).txt

function strAdd(sNum1, sNum2) {
    /*增加一位数位以记录最高位进一的情况*/
    var sNum1 = ['0', sNum1].join(''), sNum2 = ['0', sNum2].join('');

    /*给短的数字字符串加补0*/
    var len1 = sNum1.length, len2 = sNum2.length,
        zeroArr = function (len) {
            var arr = new Array(len), i = len;
            while (i--) { arr[i] = 0; }
            return arr;
        };

    if (len1 > len2) {
        var arrTemp = zeroArr(len1 - len2);
        arrTemp.push(sNum2),
            sNum2 = arrTemp.join('');
    }
    else if (len2 > len1) {
        var arrTemp = zeroArr(len2 - len1);
        arrTemp.push(sNum1),
            sNum1 = arrTemp.join('');
    }


    /*将字符串转换为数组，以相应数位来相加*/
    var arr1 = sNum1.split(''), arr2 = sNum2.split('');

    var arrAddRes = new Array(arr1.length), i = arr1.length;

    var andone = 0, // 低位相加是否进一
        cur1, cur2, curAdd;

    while (i--) {
        cur1 = +arr1[i], cur2 = +arr2[i];
        curAdd = cur1 + cur2 + andone;
        if (10 > curAdd)
            arrAddRes[i] = curAdd,
                andone = 0;
        else
            arrAddRes[i] = +curAdd.toString().slice(1, 2),
                andone = 1;
    }

    if (!andone) { // 最后是否进一，否则截取前面的0
        arrAddRes.splice(0, 1);
    }
    return [String(arrAddRes.join(''))];
}