#prefer-set-has

#Configuration

import { defineConfig, unicornPlugin } from '@rslint/core';

export default defineConfig([
  unicornPlugin.configs.recommended,
  {
    rules: {
      'unicorn/prefer-set-has': 'error',
    },
  },
]);

#Rule Details

Prefer Set#has() over Array#includes() when checking for existence or non-existence.

Set#has() is faster than Array#includes(). When an array variable binding is used only for existence checks (and, optionally, a few other supported references), this rule recommends declaring it as a Set instead. let and var bindings qualify as well as const; a binding that is reassigned is excluded by its own reference analysis, not by the declaration keyword.

Examples of incorrect code for this rule:

const array = [1, 2, 3];
const hasValue = value => array.includes(value);

Examples of correct code for this rule:

const set = new Set([1, 2, 3]);
const hasValue = value => set.has(value);

An array with supported extra references can also be converted when it has more than one includes() lookup. The array must be a plain literal with only unique, statically known primitive or null values, and no holes, spreads, or -0. Supported extra references are for…of, array spread, call or constructor argument spread, .length, and .forEach() with a one-parameter arrow function.

// Incorrect
const array = [1, 2, 3];
for (const item of array) {
	console.log(item);
}

const length = array.length;
const hasValue = value => array.includes(value);

// Correct
const set = new Set([1, 2, 3]);
for (const item of set) {
	console.log(item);
}

const length = set.size;
const hasValue = value => set.has(value);

An array that is only checked once is left alone:

// Correct
const array = [1, 2, 3];
const hasOne = array.includes(1);

#Options

Type: object

#minimumItems

Type: integer
Default: 0

The minimum known array size before Set#has() is enforced. When this option is greater than 0, the rule only reports arrays with a statically known size.

{ "unicorn/prefer-set-has": ["error", { "minimumItems": 5 }] }

Examples of incorrect code for this rule with { "minimumItems": 5 }:

const array = [1, 2, 3, 4, 5];
const hasValue = value => array.includes(value);

Examples of correct code for this rule with { "minimumItems": 5 }:

const array = [1, 2, 3, 4];
const hasValue = value => array.includes(value);

#Original Documentation

• unicorn/prefer-set-has