# prefer-set-methods

📝 Prefer `Set` methods for Set operations.

💼🚫 This rule is enabled in the ✅ `recommended` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config). This rule is _disabled_ in the ☑️ `unopinionated` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config).

🔧💡 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix) and manually fixable by [editor suggestions](https://eslint.org/docs/latest/use/core-concepts#rule-suggestions).

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Prefer modern `Set` methods over manually composing Sets with spread arrays and filters.

## Examples

```js
// ❌
const union = new Set([...set, ...otherSet]);

// ✅
const union = set.union(otherSet);
```

```js
// ❌
const intersection = [...set].filter(value => otherSet.has(value));

// ✅
const intersection = set.intersection(otherSet);
```

```js
// ❌
const difference = [...set].filter(value => !otherSet.has(value));

// ✅
const difference = set.difference(otherSet);
```

The `new Set([...set, ...otherSet])` case is autofixed only when every spread operand is known to be a `Set` or `ReadonlySet`, and the operands are safe to reuse in the replacement.

```js
// ✅
new Set([...iterable, ...otherIterable]);
```

Intersection and difference filter patterns are reported as suggestions instead of autofixes because bare filters produce arrays. Direct `new Set([...set].filter(…))` wrappers are also suggestions: `intersection()` can change Set iteration order, and `difference()` follows the same opt-in model for consistency. The rule only reports bare filter calls and direct `new Set([...set].filter(…))` wrappers.