An ESLint plugin to write custom rules with JavaScript functions.

Index

- Index
- Installation
- Write function rules inline
- Or import function rules from modules
- Define multiple function rules with custom prefix
- License

Installation

``sh


npm


npm install --save-dev eslint-plugin-function-rule
`

Write function rules inline

`ts
// eslint.config.ts

import type { Rule } from "eslint";
import { functionRule } from "eslint-plugin-function-rule";
import { defineConfig } from "eslint/config";

export default defineConfig(
{
files: ["*/.ts"],
rules: {
"function-rule/function-rule": "error",
},
plugins: {
"function-rule": functionRule((context) => {
return {
DebuggerStatement(node) {
context.report({
node,
message: "Remove 'debugger' from code.",

fix(fixer) {
return fixer.remove(node);
},
});
},
};
}),
},
},
);
`

Or import function rules from modules

`ts
// no-null.ts

import type { Rule } from "eslint";

export function noNull(options?: { enableAutoFix?: boolean; enableSuggest?: boolean }) {
const { enableAutoFix = false, enableSuggest = false } = options ?? {};
return (context: Rule.RuleContext): Rule.RuleListener => {
return {
Literal(node) {
if (node.raw !== "null" || node.parent.type !== "BinaryExpression") return;
function fix(fixer: Rule.RuleFixer) {
return fixer.replaceText(node, "undefined");
}
context.report({
node: node.parent,
message: "Avoid using 'null'; Use 'undefined' instead.",
...enableAutoFix ? { fix } : {},
...enableSuggest ? { suggest: [{ fix, desc: "Replace with 'undefined'." }] } : {},
});
},
};
};
}
`

`ts
// eslint.config.ts

import { functionRule } from "eslint-plugin-function-rule";
import { defineConfig } from "eslint/config";
import { noNull } from "./no-null.ts";

export default defineConfig(
{
files: ["*/.ts"],
rules: {
"function-rule/function-rule": "error",
},
plugins: {
"function-rule": functionRule(noNull({ enableAutoFix: true })),
},
},
);
`

Define multiple function rules with custom prefix

`ts
// eslint.config.ts

import { functionRule } from "eslint-plugin-function-rule";
import { defineConfig } from "eslint/config";

export default defineConfig(
{
files: ["*/.ts"],
rules: {
"custom-1/function-rule": 1,
"custom-2/function-rule": 2,
},
plugins: {
"custom-1": functionRule((context) => {
return {
CallExpression(node) {
if (context.sourceCode.getText(node.callee) === "Date.now") {
context.report({
node,
message: "Don't use 'Date.now'.",
});
}
},
};
}),
"custom-2": functionRule((context) => {
return {
CallExpression(node) {
if (context.sourceCode.getText(node.callee) === "Math.random") {
context.report({
node,
message: "Don't use 'Math.random()'.",
});
}
},
};
}),
},
},
);
``

License

This project is licensed under the MIT License - see the LICENSE file for details.

This project is and will continue to maintain that 90% of the code is written by humans.