oxc-project/oxc · error · OxcDiagnostic

Prefer `Date.now()` over `new Date().{bad_method}()`

Error message

Prefer `Date.now()` over `new Date().{bad_method}()`

What it means

Diagnostic from the unicorn/prefer-date-now lint rule. It fires when code calls a timestamp-returning method (e.g. getTime(), valueOf()) or otherwise coerces a freshly constructed `new Date()` with no arguments, instead of calling `Date.now()` directly. `new Date()` allocates a Date object only to read the current epoch time; `Date.now()` returns the same milliseconds since the Unix epoch without the allocation. It is a style/performance suggestion, not a runtime error.

Source

Thrown at crates/oxc_linter/src/rules/unicorn/prefer_date_now.rs:19

use oxc_ast::{
    AstKind,
    ast::{Argument, Expression},
};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::{GetSpan, Span};
use oxc_syntax::operator::{AssignmentOperator, BinaryOperator, UnaryOperator};

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

fn prefer_date_now(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Prefer `Date.now()` over `new Date()`")
        .with_help("Change to `Date.now()`.")
        .with_label(span)
}

fn prefer_date_now_over_methods(span: Span, bad_method: &str) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("Prefer `Date.now()` over `new Date().{bad_method}()`"))
        .with_help("Change to `Date.now()`.")
        .with_label(span)
}

fn prefer_date_now_over_number_date_object(span: Span, kind: &str) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("Prefer `Date.now()` over `{kind}(new Date())`"))
        .with_help("Change to `Date.now()`.")
        .with_label(span)
}

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

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Prefers use of `Date.now()` over `new Date().getTime()` or `new Date().valueOf()`.
    ///

View on GitHub (pinned to e1e7af627c)

Solutions

1. Replace `new Date().getTime()` with `Date.now()`
2. Replace `new Date().valueOf()` with `Date.now()`
3. Apply the rule's auto-fix, which rewrites the expression to `Date.now()`

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/unicorn/prefer_date_now.rs:19 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/d77e0d3ea21975df. Report an issue: GitHub.