为什么我不能用 Webpack 在我的捆绑代码中记录 `process.env`？

Question

I'm adding those environment variables to my bundle using Dotenv and DefinePlugin() .

webpack.config.js

new Dotenv(),
new webpack.DefinePlugin({
  "process.env.TEST_ENV": JSON.stringify("xxx")
}),

Dotenv loads a .env file with a bunch of environment variables. It's all working fine.

Webpack also injects by default NODE_ENV based on the mode you set in the webpack.config.js .

This is working fine and I'm able to read both NODE_ENV and TEST_ENV from my compiled and bundled code.

index.js

const { NODE_ENV, TEST_ENV } = process.env;

console.log(`process.env: ${JSON.stringify(process.env)}`);
console.log(`NODE_ENV: ${JSON.stringify(NODE_ENV)}`);
console.log(`TEST_ENV: ${JSON.stringify(TEST_ENV)}`);

I can successfully access and log both variables NODE_ENV and TEST_ENV from the process.env object, as you can see from the image above.

But when I try to log process.env itself, it logs an empty object {} , as you can also see from the picture.

Why is that? Why can't I log process.env just like I did with its properties NODE_ENV and TEST_ENV ?

Answer 1

From: https://webpack.js.org/plugins/define-plugin/

Given the fact that DefinePlugin does a direct replacement on your code, when you do this:

webpack.config.js

new webpack.DefinePlugin({
  "process.env.SOME_VARIABLE": JSON.stringify("SOME_VALUE")
});

And you call it in your code like this:

index.js

const SOME_VARIABLE = process.env.SOME_VARIABLE;

Webpack will transpile it as:

const SOME_VARIABLE = "SOME_VALUE"

It completely replaces the process.env.SOME_VARIABLE for the string "SOME_VALUE" . That's also why you need the JSON.stringify("SOME_VALUE") call. Because otherwise you would get const SOME_VARIABLE = SOME_VALUE , without the string quotes, and you'll get the SOME_VALUE is not defined error.

That's why you can't log or destructure process.env in your bundled code.