# Prefer `.some(…)` over `.filter(…).length` check and `.{find,findLast,findIndex,findLastIndex}(…)`

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

🔧💡 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).

<!-- end auto-generated rule header -->
<!-- Do not manually modify this header. Run: `npm run fix:eslint-docs` -->

Prefer using [`Array#some`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/some) over:

- Non-zero length check on the result of [`Array#filter()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter).

We only check `.filter().length > 0` and `.filter().length !== 0`. These two non-zero length check styles are allowed in [`unicorn/explicit-length-check`](./explicit-length-check.md#options) rule. It is recommended to use them together.

- Using [`Array#find()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find) or [`Array#findLast()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findLast) to ensure at least one element in the array passes a given check.

- Comparing the result of [`Array#find()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find)  or [`Array#findLast()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findLast) with `undefined`.

- Using [`Array#findIndex()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex) or [`Array#findLastIndex()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findLastIndex) to ensure at least one element in the array passes a given check.

This rule is fixable for `.filter(…).length` checks and `.{findIndex,findLastIndex}(…)`.

This rule provides a suggestion for `.{find,findLast}(…)`.

## Examples

```js
// ❌
const hasUnicorn = array.filter(element => isUnicorn(element)).length > 0;

// ❌
const hasUnicorn = array.filter(element => isUnicorn(element)).length !== 0;

// ❌
const hasUnicorn = array.filter(element => isUnicorn(element)).length >= 1;

// ❌
const hasUnicorn = array.find(element => isUnicorn(element)) !== undefined;

// ❌
const hasUnicorn = array.find(element => isUnicorn(element)) != null;

// ✅
const hasUnicorn = array.some(element => isUnicorn(element));
```

```js
// ❌
if (array.find(element => isUnicorn(element))) {
	// …
}

// ✅
if (array.some(element => isUnicorn(element))) {
	// …
}
```

```js
// ❌
const foo = array.find(element => isUnicorn(element)) ? bar : baz;

// ✅
const foo = array.find(element => isUnicorn(element)) || bar;
```

```js
// ❌
const hasUnicorn = array.findLast(element => isUnicorn(element)) !== undefined;

// ❌
const hasUnicorn = array.findLast(element => isUnicorn(element)) != null;

// ❌
const hasUnicorn = array.findIndex(element => isUnicorn(element)) !== -1;

// ❌
const hasUnicorn = array.findLastIndex(element => isUnicorn(element)) !== -1;
```

```js
// ❌
const foo = array.findLast(element => isUnicorn(element)) ? bar : baz;
```

```js
// ✅
const foo = array.findLast(element => isUnicorn(element)) || bar;
```

```vue
<template>
	<!-- ❌ -->
	<div v-if="array.find(element => isUnicorn(element))">Vue</div>

	<!-- ❌ -->
	<div v-if="array.filter(element => isUnicorn(element)).length > 0">Vue</div>

	<!-- ✅ -->
	<div v-if="array.some(element => isUnicorn(element))">Vue</div>
</template>
```

```vue
<template>
	<!-- ❌ -->
	<div v-if="array.findLast(element => isUnicorn(element))">Vue</div>
</template>
```