useObjectSpread

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

<Tabs> <TabItem label="JavaScript (and super languages)" icon="seti:javascript"> ## Summary - Rule available since: `v2.0.0` - Diagnostic Category: [`lint/style/useObjectSpread`](/reference/diagnostics#diagnostic-category) - This rule isn't recommended, so you need to enable it. - This rule has a [**safe**](/linter/#safe-fixes) fix. - The default severity of this rule is [**information**](/reference/diagnostics#information). - Sources: - Same as [`prefer-object-spread`](https://eslint.org/docs/latest/rules/prefer-object-spread) - Inspired from [`e18e/prefer-spread-syntax`](https://github.com/e18e/eslint-plugin)

How to configure

json

{
	"linter": {
		"rules": {
			"style": {
				"useObjectSpread": "error"
			}
		}
	}
}

Description

Prefer object spread over Object.assign() when constructing new objects.

Object spread syntax is more concise, more readable, and performs better than Object.assign() when creating a new object from existing objects. It also has better TypeScript integration.

Examples

Invalid

Object.assign({}, foo);

<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/use-object-spread">lint/style/useObjectSpread</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ℹ Object spread syntax is more concise, readable, and performs better than Object.assign. > 1 │ Object.assign({}, foo); │ ^^^^^^^^^^^^^ 2 │ ℹ Safe fix: Replace Object.assign({...}, <object>) with { ...<object> }. 1 │ - Object.assign({},·foo); 1 │ + ({...foo,}); 2 2 │ </code></pre>

Object.assign({}, { foo: 'bar' });

<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/use-object-spread">lint/style/useObjectSpread</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ℹ Object spread syntax is more concise, readable, and performs better than Object.assign. > 1 │ Object.assign({}, { foo: 'bar' }); │ ^^^^^^^^^^^^^ 2 │ ℹ Safe fix: Replace Object.assign({...}, <object>) with { ...<object> }. 1 │ - Object.assign({},·{·foo:·'bar'·}); 1 │ + ({foo:·'bar'·,}); 2 2 │ </code></pre>

Object.assign({ foo: 'bar' }, baz);

<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/use-object-spread">lint/style/useObjectSpread</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ℹ Object spread syntax is more concise, readable, and performs better than Object.assign. > 1 │ Object.assign({ foo: 'bar' }, baz); │ ^^^^^^^^^^^^^ 2 │ ℹ Safe fix: Replace Object.assign({...}, <object>) with { ...<object> }. 1 │ - Object.assign({·foo:·'bar'·},·baz); 1 │ + ({foo:·'bar'·,...baz,}); 2 2 │ </code></pre>

Object.assign({}, baz, { foo: 'bar' });

<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/use-object-spread">lint/style/useObjectSpread</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ℹ Object spread syntax is more concise, readable, and performs better than Object.assign. > 1 │ Object.assign({}, baz, { foo: 'bar' }); │ ^^^^^^^^^^^^^ 2 │ ℹ Safe fix: Replace Object.assign({...}, <object>) with { ...<object> }. 1 │ - Object.assign({},·baz,·{·foo:·'bar'·}); 1 │ + ({...baz,foo:·'bar'·,}); 2 2 │ </code></pre>

Valid

({ ...foo });

({ ...baz, foo: 'bar' });

Modifying an existing object is allowed:

Object.assign(foo, { bar: baz });

</TabItem> </Tabs>

How to configure

Description

Examples

Invalid

Valid

Related links