JavaScript fun: Add a large integer string

Many languages provide native support for adding two large integer strings. For example, Java provides the BigInteger class, and JS does not support this, so we have to rely on our own implementation. Many languages provide native support for adding two large integer strings.

For example, Java provides the BigInteger class, and JS does not support this, so we have to rely on our own implementation.

The following string addition function receives two string parameters and returns the result after they are added. It is also a string.

The main idea is to add and carry by bit, and there are a lot of details to consider when implementing it.

Function sumStrings (a, B) {// alignment a and B by adding zero // if a is shorter than B, then fill a with zero while (. length <B. length) {a = "0" + a;} // If B is shorter than a, then the while (B. length <. length) {B = "0" + B;} // whether the input var addOne = 0; // result array var result = []; // Add for (var I =. length-1; I> = 0; I --) {var c1 =. charAt (I)-0; var c2 = B. charAt (I)-0; var sum = c1 + c2 + addOne; // if the number is greater than 9, carry if (sum> 9) {result. unshift (sum-10); addOne = 1;} else {res Ult. unshift (sum); addOne = 0 ;}// handle the following situations: // "99" + "11" => "110" // It still needs to carry if (addOne) {result. unshift (addOne);} // handle the following situations // "01" + "01" => "2" // instead of "02 ", so remove the first "0" if (! Result [0]) {result. splice (0, 1);} return result. join ("");}

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