## Intro 🌐

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 Exercise❗

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, another `7 kyu`

kata,

meaning we slightly increase the difficulty.

Source: Codewars

Write a function `mergeArrays`

, that accepts two parameters: `a`

and `b`

.

Given two arrays, e.g. `[9, 10, 11]`

and `["a"]`

, return an array that combines both arrays by alternatingly taking elements from each array in turn, e.g. `[9, "a", 10, 11]`

.

Every element in the arrays is either a string or a number.

Input: two arrays.

Output: one array.

## Thinking about the Solution 💭

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:

- Take the 1st element of the 1st array
- Take the 1st element of the 2nd array
- Take the 2nd element of the 1st array
- Take the 2nd element of the 2nd array
- Do this [length of the longer array] amount times; in JavaScript, you get
`undefined`

, if there is no value at a specific index in an array - Filter out every
`undefined`

value

Example:

- Input:
`[9, 10, 11], ["a"]`

- Take the 1st element of the 1st array:
`9`

- Take the 1st element of the 2nd array:
`"a"`

- Take the 2nd element of the 1st array:
`10`

- Take the 2nd element of the 2nd array: nothing here =>
`undefined`

- Take the 3rd element of the 1st array:
`11`

- Take the 3rd element of the 2nd array: nothing here =>
`undefined`

- Filter out every
`undefined`

value:`[9, "a", 10, 11]`

- Output:
`[9, "a", 10, 11]`

✅

## Implementation ⛑

```
function mergeArrays(a, b) {
const maxLength = Math.max(a.length, b.length);
let result = [];
for (let i = 0; i < maxLength; i++) {
result.push(a[i]);
result.push(b[i]);
}
return result.filter((value) => value !== undefined);
}
```

### Result

```
console.log(mergeArrays([9, 10, 11], ["a"]));
// [9, "a", 10, 11] ✅
console.log(mergeArrays([1], ["a", "b"]));
// [1, "a", "b"] ✅
```

## Playground ⚽

You can play around with the code here

## Next Part ➡️

Great work!

We learned how to use `Math.max`

, `filter`

, `undefined`

.

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 📖

## Questions ❔

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

## Top comments (3)

There's no good reason to limit ourselves to two, and no particularly good reason to post-filter.