What is “Linting”?
Linting is a process of checking source code for suspicious or non-portable constructs. Or at least one definition… 
Some may say that linting isn’t worth the effort.  I personally, disagree…
Linting provides a way to enforce code style standards. It can be hard to enforce code style standards on a team sometimes. People disagree with how things should be styled, they may have habits for their own style methods already, some even forget the standards exist.
Another great benefit is keeping your source lean. In ESLint at least, you can configure it to flag variables that are unused. It sounds obvious that you would just remove those variables. But in large files of source, it may be difficult to see the variable is no longer used after an update.
Tech Company Base Rules
My favorite part about their documentation is where they explain why they have implemented specific rules.
You’ll likely need to install a few modules if you’re using Node.JS but these rules will get you started.  I use the ESLint extension published by Dirk Baeumer and have had no complaints. 
 – What is “Linting”? – https://stackoverflow.com/questions/8503559/what-is-linting
 – eslint-config-airbnb-base – https://www.npmjs.com/package/eslint-config-airbnb-base
 – ESLint – Visual Studio Marketplace – https://marketplace.visualstudio.com/items?itemName=dbaeumer.vscode-eslint
 – What’s the difference between using “let” and “var” to declare a variable? – https://stackoverflow.com/questions/762011/whats-the-difference-between-using-let-and-var-to-declare-a-variable