Linting with ESLint

Finally, we should take care to maintain a consistent code style throughout our project. Code styles are subjective, stylistic choices that do not alter the function of the program, for example, whether to use spaces or tabs, or whether to use camelCase or underscore_case when naming variables.

Having a consistent code style is important for the following reasons:

• It makes the code more readable.
• When working with others, contributors may override each other's style changes. For instance, contributor A may change all string literals to using single-quotes, and contributor B may change it back to double-quotes in a subsequent commit. This is a problem because:
  
  • Time and effort are wasted
  • It can lead to ill-feelings because no one likes their work being overwriten
  • Changes become hard to review, and the pertinent changes may be submerged under the stylistic changes.

Once a set of code style rules is defined, a linter can be used to enforce those rules. A linter is a static analysis tool that scans your code and identifies code styles that do not adhere to those rules, as well as identifying potential bugs that arise due to syntax errors.

ESLint is an open source linter for JavaScript. To use it, you would first document your rules inside a configuration file named .eslintrc. It is designed to be pluggable, which means developers can override the default rules and compose their own set of code style rules. Any violations can also be given a severity level of warning or error. It also provides useful features such as the --init flag, which initiates a wizard to help you compose your configuration file, as well as the --fix flag, which automatically fixes any violations that do not require human intervention.