JavaScript has a handful of methods to help search and filter Arrays. The methods vary depending upon if you would like to search using an item or a predicate as well as whether you need to return the item(s), index, or a Boolean.

JavaScript有一些方法可以帮助搜索和过滤数组。 这些方法取决于您是否要使用item或predicate进行搜索以及是否需要返回item(s) ， index或Boolean 。

视频 (Video)

If you prefer to consume this content in video form, then this is for you.

如果您喜欢以视频​​形式使用此内容，那么这是给您的。

什么是谓词？ (What is a Predicate?)

A predicate is just a fancy word for a function that takes an item and returns a Boolean whether the item passes some condition.

predicate只是一个函数的奇特词，该函数接受一个item并在item是否通过某些条件时返回Boolean 。

The isEven function is an example of a predicate that takes a number and returns true if the number is even.

isEven函数是predicate一个示例，该predicate采用数字，如果数字为偶数，则返回true 。

const isEven = number => number % 2 === 0

搜索多个项目 (Searching for Multiple Items)

。过滤 (.filter)

takes a predicate and returns an Array of all matching items.

接受一个predicate并返回所有匹配项的数组。

const numbers = [1, 2, 3, 4, 5]const isEven = number => number % 2 === 0const isLessThanZero = number => number < 0numbers.filter(isEven) //=> [2, 4]numbers.filter(isLessThanZero) //=> []

每个 (.every)

also searches for multiple items, see implementation below.

还搜索多个项目，请参见下面的实现。

查找第一个匹配项 (Find First Matching Item)

。找 (.find)

takes a predicate and returns the first matching item or undefined.

接受predicate并返回第一个匹配项或undefined 。

const numbers = [1, 2, 3, 4, 5]const isEven = number => number % 2 === 0const isLessThanZero = number => number < 0numbers.find(isEven) //=> 2numbers.find(isLessThanZero) //=> undefined

查找匹配项的索引 (Find The Index of Matching Item)

.findIndex (.findIndex)

takes a predicate and returns the Index or -1.

接受一个predicate并返回Index或-1 。

const numbers = [1, 2, 3, 4, 5]const isEven = number => number % 2 === 0const isLessThanZero = number => number < 0numbers.findIndex(isEven) //=> 1numbers.findIndex(isLessThanZero) //=> -1

。指数 (.indexOf)

takes an item (and optional start) and returns the Index or -1.

接受一个item (和可选的start )并返回Index或-1 。

const numbers = [1, 2, 3, 4, 5]numbers.indexOf(2) //=> 1numbers.indexOf(9) //=> -1

.lastIndexOf (.lastIndexOf)

same as indexOf, but searches in reverse.

与indexOf相同，但反向搜索。

如果存在则返回一个布尔值 (Return a Boolean if Exists)

Sometimes you only need to know whether or not items match.

有时，您只需要知道项目是否匹配即可。

.includes (.includes)

takes an item and returns true if all items match.

接受一个item ，如果所有项目都匹配，则返回true 。

const numbers = [1, 2, 3, 4, 5]numbers.includes(2) //=> truenumbers.includes(9) //=> false

每个 (.every)

takes a predicate and returns true if all items match.

接受一个predicate ，如果所有项目都匹配，则返回true 。

const numbers = [1, 2, 3, 4, 5]const isEven = number => number % 2 === 0const isGreaterThanZero = number => number > 0numbers.every(isEven) //=> falsenumbers.every(isGreaterThanZero) //=> true

。一些 (.some)

takes a predicate and returns true if at least one items matches.

接受一个predicate ，如果至少一项匹配，则返回true 。

const numbers = [1, 2, 3, 4, 5]const isEven = number => number % 2 === 0const isLessThanThanZero = number => number < 0numbers.some(isEven) //=> truenumbers.some(isLessThanThanZero) //=> false

额外信用 (Extra Credit)

Some of the predicates also include extra information like the index and the array. Read the documentation for each method to discover all of these features.

一些predicates还包括额外信息，例如index和array 。 阅读每种方法的文档以发现所有这些功能。

Example:

例：

const numbers = [1, 2, 3, 4, 5]numbers.filter((item, index, array) => { /* code here */})

摘要 (Summary)

JavaScript contains many different methods for searching Arrays. Some search for explicit items, while others use a predicate to match. Some methods return items, while others may return an index or a Boolean.

JavaScript包含许多用于搜索数组的不同方法。 一些搜索显式项目，而另一些使用predicate进行匹配。 一些方法返回项目，而其他方法则可能返回索引或布尔值。

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使用Bit共享和管理可重复使用的React组件 (Share & Manage Reusable React Components with Bit)

Use Bit (Github) to share, document, and manage reusable components from different projects. It’s a great way to increase code reuse, speed up development, and build apps that scale.

使用Bit ( Github )共享，记录和管理来自不同项目的可重用组件。 这是增加代码重用，加速开发并构建可扩展应用程序的好方法。

Exploring React components shared from different projects to Bit.dev 探索从不同项目共享到 Bit.dev的 React组件

翻译自: https://blog.bitsrc.io/8-methods-to-search-javascript-arrays-fadbce8bea51