LINTERS AND FORMATTERS

Part of the problem with JavaScript debugging is that there aren't many IDEs that automatically indicate syntax errors as you type. Most developers write some code and then load it into a browser to look for errors. You can significantly reduce the instances of such errors by validating your JavaScript code before deployment. Linters check basic syntax and provide warnings about style.

Formatters are tools that implicitly understand the syntactical rules of a language and use a collection of indentation, whitespace, line wrap, and other strategies to give you the capability to automatically neatly organize the content of a file. Formatters will never break or modify the code or semantic meaning of the code, as they are aware of the kinds of modifications that would serve to alter the execution.

ESLint

ESLint is an open-source JavaScript linting utility originally developed by none other than the author of early editions of this very book, Nicholas Zakas...