https://github.com/HKalbasi/eslint-plugin-toplevel

An eslint plugin for disallow side effect at module toplevel
https://github.com/HKalbasi/eslint-plugin-toplevel

Last synced: 3 months ago
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An eslint plugin for disallow side effect at module toplevel

• Host: GitHub
• URL: https://github.com/HKalbasi/eslint-plugin-toplevel
• Owner: HKalbasi
• License: gpl-3.0
• Created: 2019-09-09T10:59:19.000Z (about 5 years ago)
• Default Branch: master
• Last Pushed: 2024-03-12T21:24:00.000Z (8 months ago)
• Last Synced: 2024-04-14T11:15:03.025Z (7 months ago)
• Language: JavaScript
• Size: 34.2 KB
• Stars: 17
• Watchers: 3
• Forks: 2
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-eslint - toplevel - An eslint plugin for disallow side effect at module toplevel. (Plugins / Practices and Specific ES Features)

README

        
# eslint-plugin-toplevel

An eslint plugin for disallow side effect at module toplevel

## Why?

Side effect in toplevel of a module are hard to reason, and [behave diffrently](https://developpaper.com/explain-the-difference-between-commonjs-and-es6-modules-in-cyclic-loading-processing/) in CommonJS and ES6 modules. And there is no way to import a module without it's side effects. Solution is simple: **Don't make side effect at top level**.

## Example

### Bad

```JS

console.log('hello world');

let s=0;

for (let i=0;i<10;i++) {

  s += i;

}

console.log(s);

fetch('/api').then(res=>res.text()).then(console.log);

```

### Good

```JS

export async function main() {

  console.log('hello world');

  let s=0;

  for (let i=0;i<10;i++) {

    s += i;

  }

  console.log(s);

  const res = await fetch('/api');

  console.log(await res.text());

}

```

And then in html:

```HTML

  import { main } from "/js/main.mjs";

  main();

```

Or in nodejs make a runner.mjs file:

```JS

import { main } from "./main.mjs";

main();

```

## Rules

There are three rules in this plugin:

### no-toplevel-var

Disallow var usage at toplevel module.  

Goal of this rule is to prevent modules to have internal state.

### no-toplevel-let

similiar to `no-toplevel-var`

### no-toplevel-side-effect

Disallow any side effect at top level

## Contributing

I'd love to accept your patches and contributions to this project.  

There are many ways you can contribute. For example:

* Add tests

* Fix bugs

* Add option to ignore `module.exports` assigns in `no-toplevel-side-effect` rule

* Add good documention