JavaScript: Two positive integers as string, return their sum

Last update on April 22 2023 12:21:29 (UTC/GMT +8 hours)

JavaScript Math: Exercise-77 with Solution

Write a JavaScript program to compute the sum of two non-negative integers num1 and num2 represented by strings.

Test Data:
("123", "123") -> 246
("45", "100") -> 145

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript program to Two positive integers as string, return their sum</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function test(n1, n2) {
    var str = '';
    var carry = 0;
    var num1 = n1.length -1;
    var num2 = n2.length -1;
    var sum_of_two

    while(num1 >= 0 || num2 >= 0){
        sum_of_two = (parseInt(n1[num1]) || 0) + (parseInt(n2[num2]) || 0) 
        sum_of_two += carry ? 1:0
        
        if(sum_of_two > 9){
            carry = 1;
            str = sum_of_two %10 + str 
        }else{
            str = sum_of_two  + str;
            carry = 0
        }
        num1--;
        num2--
    }
    if(carry){str = 1+ str}
    return str
};
console.log(test("123", "123"));
console.log(test("45", "100"));

Sample Output:

246
145

Flowchart:

$JavaScript: Two positive integers as string, return their sum.$

Live Demo:

See the Pen javascript-math-exercise-77 by w3resource (@w3resource) on CodePen.

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