JS implements multiplication of two large numbers (integers)_javascript skills

Large numbers, that is, numbers that exceed the maximum range of numbers that can be represented by language. At this time, the numbers can only be represented by strings. So how to multiply two large numbers? I implemented it with JS, the code is as follows:

Copy code The code is as follows:

console. log(bigMut("567", "1234")); // 699678
function bigMut(big, common) {
big = "";
common = "";
if (big .length < common.length) {
big = [common, common = big][0];
}
big = big.split("").reverse();
var oneMutManyRes = [];
var i = 0,
len = big.length;
for (; i < len; i ) {
oneMutManyRes[oneMutManyRes.length] = oneMutMany(big[ i], common) getLenZero(i);
}
var result = oneMutManyRes[0];
for (i = 1, len = oneMutManyRes.length; i < len; i ) {
result = bigNumAdd(result, oneMutManyRes[i]);
}
return result;
}
function getLenZero(len) {
len = 1;
var ary = [ ];
ary.length = len;
return ary.join("0");
}
function oneMutMany(one, many) {
one = "";
many = "";
if (one.length != 1) {
one = [many, many = one][0];
}
one = parseInt(one, 10);
var i = 0,
len = many.length,
resAry = [],
addTo = 0,
curItem,
curRes,
toSave;
many = many.split("").reverse();
for (; i <= len; i ) {
curItem = parseInt(many[i] || 0, 10);
curRes = curItem * one addTo;
toSave = curRes % 10;
addTo = (curRes - curRes % 10) / 10;
resAry.unshift(toSave);
}
if ( resAry[0] == 0) {
resAry.splice(0, 1);
}
return resAry.join("");
}
function bigNumAdd(big, common ) {
big = "";
common = "";
var maxLen = Math.max(big.length, common.length),
bAry = big.split(""). reverse(),
cAry = common.split("").reverse(),
i = 0,
addToNext = 0,
resAry = [],
fn,
sn,
sum;
for (; i <= maxLen; i ) {
fn = parseInt(bAry[i] || 0);
sn = parseInt(cAry[i] || 0);
sum = fn sn addToNext;
addToNext = (sum - sum % 10) / 10;
resAry.unshift(sum % 10);
}
if ( resAry[0] == 0) {
resAry.splice(0, 1);
}
return resAry.join("");
}