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.

The rule reports a call of a charCodeAt method in every spelling: s.charCodeAt(0), s['charCodeAt'](0), an optional call (s?.charCodeAt(0)) and a non-null receiver (s!.charCodeAt(0)). It does not report codePointAt, a method chosen by a runtime key (s[method](0)), or a plain function that happens to be named charCodeAt. The rule has no options.

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

• String.prototype.charCodeAt.call(s, 0) and a reference that is called later (const at = s.charCodeAt; at.call(s, 0)) are not reported.
• String.fromCharCode() (the inverse, which String.fromCodePoint() replaces) is not in scope.

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',    },  },});