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Automatically Remove Unused Imports From Your JS Projects

Simon
Originally published at simondosda.github.io Updated on ・3 min read

Photo by The Creative Exchange.

Recently, I came across a substantial Angular project with a lot of unused imports. It is not a big deal, but it looked pretty messy, which I find to be a pity as automatically removing them is pretty straightforward.

In this article, I will show how to do so for any node-based project using ESLint. It might sound like a very cosmetic thing, and it kind of is, but I believe having too many unused imports can hurt code readability.

And as a bonus, we will also sort our imports in alphabetical order.

Add ESLint to your project

ESLint is a static code analyzer and will prevent you from making many dummy mistakes, like using undeclared variables or expecting an output from a function that doesn't have any.

It can also enforce code style rules, like the type of quotes you want to use or define if code lines should always end with semicolons, even though you will most likely use a code formatter like Prettier to take care of this.

If you haven't used it yet, you will need to add ESLint to your project. You can easily install it and generate its configuration file with npm.

npm install eslint --save-dev
npx eslint --init
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You can then check the errors and warnings from ESLint by running it in your project.

npx eslint <source-directory>
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Automatically remove unused imports

To automatically remove unused imports, we will need to add the eslint-plugin-unused-imports plugin.

Install it using npm:

npm install eslint-plugin-unused-imports --save-dev
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Then add it to your configuration file; here with the recommended rules from the author:

{
  "plugins": ["unused-imports"],
  "rules": {
    "no-unused-vars": "off",
    "unused-imports/no-unused-imports": "error",
    "unused-imports/no-unused-vars": [
      "warn",
      {
        "vars": "all",
        "varsIgnorePattern": "^_",
        "args": "after-used",
        "argsIgnorePattern": "^_"
      }
    ]
  }
}
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Now, when you run ESLint, you should see error lines saying error '<imported-var>' is defined but never used unused-imports/no-unused-imports for the files where you have unused imports. Moreover, the last line should print the following line X errors and Y warnings potentially fixable with the --fix option..

The number of errors should be superior to 0 unless you don't have any unused imports in your project. If that's the case, add some for the sake of this exercise ;).

Next, run npx eslint <project-directory> --fix and...voilà!

There should not be any unused import in your code anymore.

Bonus: sort your imports by alphabetical order

Sorting imports by alphabetical order is the last thing I want to take care of. I don't think it really matters, even though it can be part of a company or a team's rules to do so.

In any case, ESLint allows us to do this automatically, so why deprive ourselves of it?

To benefit from this feature, you need to add the sort-import rule to your ESLint configuration file.

{
  "rules": {
    ...
    "sort-imports": [
      "error",
      {
        "ignoreDeclarationSort": true
      }
  ]
}
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Unfortunately, the --fix option will not automatically fix multiple lines errors. For this reason, I prefer to set ignoreDeclarationSort to true.

It is for the best anyway because this rule provides minimal customization to order your imports. And I don't think alphabetical order at line level makes sense without considering the kind of import; you don't want your local imports mixed with third-party libraries, for instance. If you are using TSLint though, check ordered-imports that allows you to define your import order and fix multiple lines imports.

Now, running ESLint with the --fix option will reorder your multiple members' imports. For instance, import { d, a, c, b } from e; will be changed to import { a, b, c, d } from e;.

It doesn't hurt!

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