oxc-project/oxc · info · OxcDiagnostic

Use Unicode escapes instead of hexadecimal escapes.

Error message

Use Unicode escapes instead of hexadecimal escapes.

What it means

Diagnostic from the oxlint rule `unicorn/no-hex-escape`. It enforces Unicode escapes (`\u0041`, `\u{1B}`) over hexadecimal escapes (`\x41`) in string literals, template literals, and regular expressions. Both forms produce identical strings, but the `\u` forms are self-consistent and generalize to all code points, while `\xNN` only covers Latin-1. `String.raw` tagged templates are exempt because they produce literal backslash sequences, not escapes.

Source

Thrown at crates/oxc_linter/src/rules/unicorn/no_hex_escape.rs:15

use oxc_ast::{AstKind, ast::StringLiteral};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_regular_expression::{
    ast::{Character, CharacterKind},
    visit::Visit,
};
use oxc_span::Span;

use crate::{
    AstNode, context::LintContext, rule::Rule, utils::is_string_raw_tagged_template_expression,
};

fn no_hex_escape_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Use Unicode escapes instead of hexadecimal escapes.").with_label(span)
}

#[derive(Debug, Default, Clone)]
pub struct NoHexEscape;

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Enforces a convention of using [Unicode escapes](https://mathiasbynens.be/notes/javascript-escapes#unicode)
    /// instead of [hexadecimal escapes](https://mathiasbynens.be/notes/javascript-escapes#hexadecimal) for
    /// consistency and clarity.
    ///
    /// ### Why is this bad?
    ///
    /// Using hexadecimal escapes can be less readable and harder to understand
    /// when compared to Unicode escapes.
    ///
    /// ### Examples

View on GitHub (pinned to e1e7af627c)

Solutions

1. Convert to Unicode escapes: `\x1B` becomes `\u{1B}` or `\u001B`; `\x41` becomes `\u0041`
2. When you need literal backslash-x text, use String.raw`\x1B`, which the rule ignores
3. In regexes, prefer the u flag with `\u{...}` or Unicode property escapes

Example fix

// before
const ESC = '\x1B';

// after
const ESC = '\u{1B}';

When it happens

Trigger: Any `\xNN` escape in a string literal (`'\x1B[31m'`), a template literal, or a RegExp character class (`/[\x00-\x1f]/`) — except inside String.raw tagged templates.

Common situations: Terminal ANSI escape codes, binary protocol literals, regex character classes over control characters; mixed escape styles after merging code from several authors or eras.

Related errors

• Use uppercase characters for the value of the escape sequenc
• Use a regular expression literal instead of the `RegExp` con
• Use the 'v' flag.
• Use the 'u' flag.
• Passing `length` as the end argument of a `slice` call is un

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/dc14eb2a4ff76b6a. Report an issue: GitHub.