useDateNow

import { Tabs, TabItem } from '@astrojs/starlight/components';

<Tabs> <TabItem label="JavaScript (and super languages)" icon="seti:javascript"> ## Summary - Rule available since: `v1.8.0` - Diagnostic Category: [`lint/complexity/useDateNow`](/reference/diagnostics#diagnostic-category) - This rule is **recommended**, meaning it is enabled by default. - This rule has an [**unsafe**](/linter/#unsafe-fixes) fix. - The default severity of this rule is [**warning**](/reference/diagnostics#warning). - Sources: - Same as [`unicorn/prefer-date-now`](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/prefer-date-now.md) - Same as [`e18e/prefer-date-now`](https://github.com/e18e/eslint-plugin)

How to configure

json

{
	"linter": {
		"rules": {
			"complexity": {
				"useDateNow": "error"
			}
		}
	}
}

Description

Use Date.now() to get the number of milliseconds since the Unix Epoch.

Date.now() is more readable than new Date().getTime() and its variants, it also avoids unnecessary instantiation of Date object.

Examples

Invalid

const foo = new Date().getTime();

<pre class="language-text"><code class="language-text">code-block.js:1:13 <a href="https://biomejs.dev/linter/rules/use-date-now">lint/complexity/useDateNow</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ Use Date.now() instead of new Date().getTime(). > 1 │ const foo = new Date().getTime(); │ ^^^^^^^^^^^^^^^^^^^^ 2 │ ℹ Date.now() is more readable and also avoids unnecessary instantiation of Date object. ℹ Unsafe fix: Replace with Date.now(). 1 │ - const·foo·=·new·Date().getTime(); 1 │ + const·foo·=·Date.now(); 2 2 │ </code></pre>

const foo = new Date().valueOf();

<pre class="language-text"><code class="language-text">code-block.js:1:13 <a href="https://biomejs.dev/linter/rules/use-date-now">lint/complexity/useDateNow</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ Use Date.now() instead of new Date().valueOf(). > 1 │ const foo = new Date().valueOf(); │ ^^^^^^^^^^^^^^^^^^^^ 2 │ ℹ Date.now() is more readable and also avoids unnecessary instantiation of Date object. ℹ Unsafe fix: Replace with Date.now(). 1 │ - const·foo·=·new·Date().valueOf(); 1 │ + const·foo·=·Date.now(); 2 2 │ </code></pre>

const foo = +new Date();

<pre class="language-text"><code class="language-text">code-block.js:1:13 <a href="https://biomejs.dev/linter/rules/use-date-now">lint/complexity/useDateNow</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ Use Date.now() instead of new Date(). > 1 │ const foo = +new Date(); │ ^^^^^^^^^^^ 2 │ ℹ Date.now() is more readable and also avoids unnecessary instantiation of Date object. ℹ Unsafe fix: Replace with Date.now(). 1 │ - const·foo·=·+new·Date(); 1 │ + const·foo·=·Date.now(); 2 2 │ </code></pre>

const foo = Number(new Date());

<pre class="language-text"><code class="language-text">code-block.js:1:13 <a href="https://biomejs.dev/linter/rules/use-date-now">lint/complexity/useDateNow</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ Use Date.now() instead of Number(new Date()). > 1 │ const foo = Number(new Date()); │ ^^^^^^^^^^^^^^^^^^ 2 │ ℹ Date.now() is more readable and also avoids unnecessary instantiation of Date object. ℹ Unsafe fix: Replace with Date.now(). 1 │ - const·foo·=·Number(new·Date()); 1 │ + const·foo·=·Date.now(); 2 2 │ </code></pre>

const foo = new Date() * 2;

<pre class="language-text"><code class="language-text">code-block.js:1:13 <a href="https://biomejs.dev/linter/rules/use-date-now">lint/complexity/useDateNow</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ Use Date.now() instead of new Date(). > 1 │ const foo = new Date() * 2; │ ^^^^^^^^^^ 2 │ ℹ Date.now() is more readable and also avoids unnecessary instantiation of Date object. ℹ Unsafe fix: Replace with Date.now(). 1 │ - const·foo·=·new·Date()·*·2; 1 │ + const·foo·=·Date.now()*·2; 2 2 │ </code></pre>

Valid

const foo = Date.now();

const foo = Date.now() * 2;

</TabItem> </Tabs>

How to configure

Description

Examples

Invalid

Valid

Related links