Awesome
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 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
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
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:
<script type="module">
import { main } from "/js/main.mjs";
main();
</script>
Or in nodejs make a runner.mjs file:
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 inno-toplevel-side-effect
rule - Add good documention