@browserify/envify 
Selectively replace Node-style environment variables with plain strings. Available as a standalone CLI tool and a Browserify transform.
Works best in combination with @browserify/uglifyify.
Installation
If you're using the module with Browserify:
npm install @browserify/envify browserify
Or, for the CLI:
sudo npm install -g @browserify/envify
Usage
envify will replace your environment variable checks with ordinary strings -
only the variables you use will be included, so you don't have to worry about,
say, AWS_SECRET_KEY leaking through either. Take this example script:
if (process.env.NODE_ENV === "development") {
console.log('development only')
}
After running it through envify with NODE_ENV set to production, you'll
get this:
if ("production" === "development") {
console.log('development only')
}
By running this through a good minifier (e.g. terser), the above code would be stripped out completely.
However, if you bundled the same script with NODE_ENV set to development:
if ("development" === "development") {
console.log('development only')
}
The if statement will evaluate to true, so the code won't be removed.
CLI Usage
With browserify:
browserify index.js -t @browserify/envify > bundle.js
Or standalone:
envify index.js > bundle.js
You can also specify additional custom environment variables using browserify's subarg syntax, which is available in versions 3.25.0 and above:
browserify index.js -t [ @browserify/envify --NODE_ENV development ] > bundle.js
browserify index.js -t [ @browserify/envify --NODE_ENV production ] > bundle.js
Module Usage
require('@browserify/envify')
Returns a transform stream that updates based on the Node process'
process.env object.
require('@browserify/envify/custom')([environment])
If you want to stay away from your environment variables, you can supply your own object to use in its place:
var browserify = require('browserify')
, envify = require('@browserify/envify/custom')
, fs = require('fs')
var b = browserify('main.js')
, output = fs.createWriteStream('bundle.js')
b.transform(envify({
NODE_ENV: 'development'
}))
b.bundle().pipe(output)
Purging process.env
By default, environment variables that are not defined will be left untouched. This is because in some cases, you might want to run an envify transform over your source more than once, and removing these values would make that impossible.
However, if any references to process.env are remaining after transforming
your source with envify, browserify will automatically insert its shim for
Node's process object, which will increase the size of your bundle. This weighs
in at around 2KB, so if you're trying to be conservative with your bundle size
you can "purge" these remaining variables such that any missing ones are simply
replaced with undefined.
To do so through the command-line, simply use the subarg syntax and include
purge after envify, e.g.:
browserify index.js -t [ @browserify/envify purge --NODE_ENV development ]
Or if you're using the module API, you can pass _: "purge" into your
arguments like so:
b.transform(envify({
_: 'purge'
, NODE_ENV: 'development'
}))