# JavaScript Katas: Every possible sum of two digits

## Intro π

Problem solving is an important skill, for your career and your life in general.

That's why I take interesting katas of all levels, customize them and explain how to solve them.

## Understanding the Exerciseβ

First, we need to understand the exercise! If you don't understand it, you can't solve it!.

My personal method:

- Input: What do I put in?
- Output: What do I want to get out?

### Today's exercise

Today, we'll have a look at our first 7 kyu kata, meaning we slightly increase the difficulty.

Source: Codewars

Write a function `everyPossibleSum`

, that accepts one parameter: `myNumber`

.

Given a number, e.g. `1234`

,
return every possible sum of two digits, e.g. `[ 3, 4, 5, 5, 6, 7 ]`

.

For this example, we calculate:
`[ 1 + 2, 1 + 3, 1 + 4, 2 + 3, 2 + 4, 3 + 4 ]`

Input: a number.

Output: an array of numbers.

## Thinking about the Solution π

I think I understand the exercise (= what I put into the function and what I want to get out of it).

Now, I need the specific steps to get from input to output.

I try to do this in small baby steps:

- Get the single digits of the input number
- Go to the first digit and find all sums with each next digit, starting from the second
- Go to the second digit and find all sums with each next digit, starting from the third
- Do this for every digit
- Return the array with each sum in it

Example:

- Input:
`1234`

- Go to the first digit and find all sums with each next digit, starting from the second:
`1 + 2`

,`1 + 3`

,`1 + 4`

- Go to the second digit and find all sums with each next digit, starting from the third:
`2 + 3`

,`2 + 4`

- Do this for every digit:
`3 + 4`

- Return the array with each sum in it:
`[ 3, 4, 5, 5, 6, 7 ]`

- Output:
`[ 3, 4, 5, 5, 6, 7 ]`

β

## Implementation β

```
function everyPossibleSum(myNumber) {
// split up number into its digits
const split = String(myNumber) // make it a string
.split("") // split it
.map((digit) => Number(digit)); // convert each split char to a number
const sums = [];
// first number: iterate from the first to the last number
for (let first = 0; first < split.length; first++) {
// second number: iterate from the next number after the current first number to the last number
for (let second = first + 1; second < split.length; second++) {
Fiy
// save the sum in the sums array
sums.push(split[first] + split[second]);
}
}
return sums;
}
```

### Result

```
console.log(everyPossibleSum(1234));
// [ 3, 4, 5, 5, 6, 7 ] β
console.log(everyPossibleSum(81596));
// [ 9, 13, 17, 14, 6, 10, 7, 14, 11, 15 ] β
```

## Playground β½

You can play around with the code here

## Next Part β‘οΈ

Great work!

We learned how to use `String`

, `split`

, `map`

, `for`

.

I hope you can use your new learnings to solve problems more easily!

Next time, we'll solve another interesting kata. Stay tuned!

If I should solve a specific kata, shoot me a message here.

If you want to read my latest stuff, get in touch with me!

## Further Reading π

## Questions β

- How often do you do katas?
- Which implementation do you like more? Why?
- Any alternative solution?