Code Wars - Sum The Strings

Breaking down code war challenges in a simple and understandable way.

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The Problem Statement

Create a function that takes 2 integers in form of a string as an input, and outputs the sum (also as a string):

Example: (Input1, Input2 -->Output)

"4", "5" --> "9" "34", "5" --> "39" "", "" --> "0" "2", "" --> "2""-5", "3" --> "-2" // Notes: If either input is an empty string, consider it as zero.

Analysis -Breaking down the question

If we add two strings it doesn’t perform addition. Instead, it will join them together. For example, let’s take the first example of "4", "5" --> "9" -This is what we expected but we will get "45" in return.

So, Let’s see how we can solve this problem.

The Solution

Create a basic function with two strings as inputs

function sumStr(a,b) {


First, we need to convert the a, b to numbers to get the desired result. For that, we can use Number( ) to convert it to an integer.

function sumStr(a,b) {
   return Number(a)+Number(b) //The result will be 9 (refer to above example)

But we need to change it back to a string. For that, we can use toString( ) as below.

function sumStr(a,b) {
   return (Number(a)+Number(b)).toString(); //The result will be 9 (refer to above example)

sumStr("4", "5") //"9"

At this point, if the a or b is an empty string the function will return the other string. We can use if condition to check the string is empty or 0 as below.

function sumStr(a,b) {
  if (a ==0 || b==0){
    return "0"
  }else {
     return (Number(a)+ Number(b)).toString();

The function will check if the a or b is 0 and if it is true, returns 0. Otherwise, the else block will be executed.

Final Words

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