prefer-event-target

Prefer EventTarget over EventEmitter for isomorphic code. This rule is part of eslint-plugin-modernization.

Quick SummaryCopy Anchor Link

Rule DetailsCopy Anchor Link

EventTarget is available in both browsers and Node.js (v14.5+), while EventEmitter is Node.js-specific.

The rule reports Node's EventEmitter, found by where the binding comes from (events / node:events). A named or renamed import and a require destructure (plain or quoted key) are reported where they are bound. The default import (the module's default export is EventEmitter) and the required module itself (const E = require('events')) are reported where they are used, at new E() or class Bus extends E, because the same binding also reaches other events exports such as E.once. A namespace member (ev.EventEmitter) and require('events').EventEmitter are reported where they are read. require must be Node's loader, either the global or one made by createRequire.

It does not report an EventEmitter from another module (Angular's @angular/core EventEmitter is an RxJS Subject), a class the file declares itself, a member of a parameter (events.EventEmitter where events is passed in), or other events exports such as once. A named binding (import { EventEmitter }, const { EventEmitter } = require('events')) is reported once, where it is bound. An undeclared EventEmitter or events.EventEmitter is still reported by name.

ConfigurationCopy Anchor Link

Why This MattersCopy Anchor Link

ExamplesCopy Anchor Link

❌ IncorrectCopy Anchor Link

import { EventEmitter } from 'events';

class MyEmitter extends EventEmitter {
  emit(event: string) {
    super.emit(event);
  }
}

✅ CorrectCopy Anchor Link

class MyEmitter extends EventTarget {
  dispatch(type: string, detail?: unknown) {
    this.dispatchEvent(new CustomEvent(type, { detail }));
  }
}

// Usage
const emitter = new MyEmitter();
emitter.addEventListener('change', (e) => console.log(e));
emitter.dispatch('change', { value: 42 });

Configuration ExamplesCopy Anchor Link

Basic UsageCopy Anchor Link

{
  rules: {
    'modernization/prefer-event-target': 'warn'
  }
}

Related RulesCopy Anchor Link

• no-nodejs-modules - Prevent Node.js imports in browser code

Further ReadingCopy Anchor Link

• EventTarget - MDN - MDN reference
• Node.js EventTarget - Node.js docs

Known False NegativesCopy Anchor Link

The following patterns are not detected due to static analysis limitations:

Dynamic Variable ReferencesCopy Anchor Link

Why: Static analysis cannot trace values stored in variables or passed through function parameters.

// ❌ NOT DETECTED - Value from variable
const value = externalSource();
processValue(value); // Variable origin not tracked

Mitigation: Implement runtime validation and review code manually. Consider using TypeScript branded types for validated inputs.

Imported ValuesCopy Anchor Link

Why: When values come from imports, the rule cannot analyze their origin or construction.

// ❌ NOT DETECTED - Value from import
import { getValue } from './helpers';
processValue(getValue()); // Cross-file not tracked

Mitigation: Ensure imported values follow the same constraints. Use TypeScript for type safety.

Use this rule

npm install -D oxlint-plugin-modernization

{  "jsPlugins": ["oxlint-plugin-modernization"],  "rules": {    "modernization/prefer-event-target": "error"  }}

import { defineConfig } from 'vite-plus';export default defineConfig({  lint: {    jsPlugins: ['oxlint-plugin-modernization'],    rules: {      'modernization/prefer-event-target': 'error',    },  },});