mark-of-dev

👩‍💻  Advancing the globalization of __DEV__

When mark-of-dev is first loaded into a process, it sets the so-called mark of dev or global.__DEV__ to true for non-production runs and false for production runs. This package considers a run as production if and only if the value of process.env.NODE_ENV is a case-insensitive match for either prod or production. In case of a match, this package also updates process.env.NODE_ENV to the canonical production string, just as written.

mark-of-dev is conservative in that it does not make any changes when __DEV__ has already been defined and in that it prevents future changes when it defines __DEV__ as a non-configurable, non-enumerable, and non-writable property. It is liberal in that it works independent of how it is loaded. Both CommonJS and ES6 are just fine. For once, that is possible because this package's only module is executed for side effect only and thus has neither imports nor exports.

Since mark-of-dev always sets __DEV__, code may test for development runs by mentioning the mark of dev by itself

if (__DEV__) { ... }

or by making the scope explicit

if (global.__DEV__) { ... }

Personally, I prefer the former, since it is more concise and easier to locally override. In either case, you are well-advised to declare the new global

"globals": { "__DEV__": false },

and be tolerant of its underscores

"no-underscore-dangle": ["error", { "allow": ["__DEV__"] }],

so that tools such as ESLint continue to peacefully coexist with your code.

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Copyright and License

© 2018 Robert Grimm, released under the MIT license.