Modernize codebase

[SiarheiFedartsou]

👋 I did some awesome work for the Pelias project and would love for everyone to have a look at it and provide feedback.

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Here's the reason for this change 🚀

What about modernizing codebase of Pelias a bit? It should make maintenance easier.

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Here's what actually got changed 👏

• var -> const/let
• function -> arrow functions where possible
• indexOf(...) != -1 -> includes

I used Lebab to automate it.

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Here's how others can test the changes 👀

Existing tests :)

[SiarheiFedartsou]

Tbh the change is quite big and I am not sure if maintainers are okay with such size(even though there are no anything complicated), so please feel free to ask to somehow split it.

[orangejulius]

Yeah, in general we do not accept giant contributions to modernize the code.

It's basically impossible to review to ensure a bug or (even worse) a vulnerability did not sneak in.

Sorry.

[orangejulius]

Oops, sorry to be clear I did not mean to close, just comment. Don't want to seem passive-agressive :P