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no-foreach

Disallow calling forEach on configured collection types.

Targeted pattern scope​

⚠️ This rule requires type information to run. Configure type-aware linting (parserOptions.project or projectService) before enabling it.

This rule targets member calls to .forEach(...) and reports only when the receiver type matches configured collection names.

What this rule reports​

This rule reports .forEach(...) calls for configured type names (by default: Array, Map, NodeList, and Set). In codebases that standardize on explicit loops, for...of improves control-flow clarity (for example, with break, continue, and return).

Why this rule exists​

Teams that standardize on explicit loops often prefer for...of for control flow clarity (break, continue, early return) and debugger ergonomics.

❌ Incorrect​

const answers = [42, 54];
answers.forEach((answer) => console.log(answer));

✅ Correct​

const answers = [42, 54];
for (const answer of answers) {
 console.log(answer);
}

Behavior and migration notes​

This rule reports only and does not provide an autofix.

Adopt gradually by enabling as warn, then migrating hot paths and shared utilities to for...of before promoting to error.

Options​

type Options = {
 types?: string[];
};

Default: { types: ["Array", "Map", "NodeList", "Set"] }

When Array is included, ReadonlyArray is also treated as matched.

types​

Use this option to control which type names are checked.

Additional examples​

const set = new Set([1, 2, 3]);
set.forEach((value) => console.log(value));
// ❌ reported with default options

const map = new Map<string, number>();
for (const [key, value] of map) {
 console.log(key, value);
}
// ✅ preferred style

ESLint flat config example​

import etcMisc from "eslint-plugin-etc-misc";

export default [
 {
  plugins: { "etc-misc": etcMisc },
  rules: {
   "etc-misc/no-foreach": ["error", { types: ["Array", "Set"] }],
  },
 },
];

When not to use it​

Disable this rule if your project intentionally favors iterator callbacks and does not enforce loop-style consistency.

Package documentation​

Rule catalog ID: R038

Further reading​

Adoption resources​

  • Start at warning level in CI, then move to error after cleanup.
  • Use focused codemods/autofix batches per package or directory.