updating function name per #200 thanks to @marzelin to clean up some issues

Add Japanese translation

updating L278 to `isActiveClient`

...you will find that those *case*... -> ..you will find that those *cases*...

fixed a grammatical typo

Fix duplicate code example

Update README.md to include explanatory function names per #200 

Add Polish translation

* translate kata pengantar / introduction
* translate variabel
* typo
* function 1/2
* 1/2 replace
* translate ### 😂
* translate Function section in Bahasa Indonesia is done
* 1/2 SOLID translation to Bahasa Indonesia
* SOLID translation to Bahasa Indonesia is Done
* translating Error Handling to bahasa indonesia is done
* well done, translated to Bahasa Indonesia
* review 1, check typo
* review 2
* just link

Capital letters in const, remove default data in class Car

Capital letters in const, remove default data in class Car

The proposed "good" way of coding was actually changing a property's name in the developers object.
While one can argue that in this case they could be the same, the point of the example was to show that you can still remove duplicated code that require *different* things.

Fixed duplicate code

Remove space before colon in object.

Object style consistency

Update README.md

'data' is never reassigned. Use 'const' instead.

...turing
Replace map method with object destructuring

There's -> There are

minor grammar edit

Hey there. As a Software Engineer who happens to be Nigerian, I think there are better ways of explaining a side effect than perpetuating stereotypes about a specific group of people. So I just made a small fix to make it more appropriate.

Use `console.error` at least as `console.log` essentially turns a thrown error into a muted console log.

In the "good" `Object.assign` example, the initial new object is redundant as the defaults are also specified in a new object.
This is a bit pedantic, and doesn't change the semantics of the example, just removes an unnecessary object creation.

The original phrase "As stated in the Gang of Four..." is semantically incorrect.
- The "Gang of Four" is a group of authors: Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides.
- They wrote a famous book: Design Patterns.
- Here, Ryan McDermott is referring to the software-design principle "you should prefer composition over inheritance."
- This principle was stated in the book, Design Patterns.
- It was not stated in the Gang of Four -- the authors themselves.

per preceding rule "ES6 constants when variable values do not change"

In the section "Functions should do one thing" this change uses
the Array.filter method to get the active clients, then emailing
those with the forEach loop.

The save method isn't returning this, so the car variable
is equal to undefined instead of a Car object.
BTW, Thanks alot for this guide.

...witch to "ES<year>/ES<edition>" when mentioning ECMAScript versions.

Something looked off about this so I did a quick check in node.
You must have been distracted at the time of writing :)

We need a better explanation for when to prefer `const` over var/let,
as this has confused many readers.

Add italian translation