prefer-code-point

Prefer String.codePointAt() over String.charCodeAt(). This rule is part of eslint-plugin-conventions.

Quick SummaryCopy Anchor Link

Rule DetailsCopy Anchor Link

charCodeAt() only works for Basic Multilingual Plane characters. codePointAt() handles all Unicode including emoji.

Why This MattersCopy Anchor Link

ExamplesCopy Anchor Link

❌ IncorrectCopy Anchor Link

const code = string.charCodeAt(0);  // Fails for emoji
'😀'.charCodeAt(0);  // Returns 55357 (wrong!)

✅ CorrectCopy Anchor Link

const code = string.codePointAt(0);  // Works for all Unicode
'😀'.codePointAt(0);  // Returns 128512 (correct!)

// Iterate over code points
for (const char of string) {
  const codePoint = char.codePointAt(0);
}

Configuration ExamplesCopy Anchor Link

Basic UsageCopy Anchor Link

{
  rules: {
    'conventions/prefer-code-point': 'warn'
  }
}

Related RulesCopy Anchor Link

• prefer-dom-node-text-content - DOM text handling

Further ReadingCopy Anchor Link

• codePointAt() - MDN - MDN reference

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-conventions

{  "jsPlugins": ["oxlint-plugin-conventions"],  "rules": {    "conventions/prefer-code-point": "error"  }}

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