爱站程序员基地There are different methods in JavaScript that you can use to search for an item in an array. Which method you choose depends on your specific use case.
您可以使用JavaScript中的不同方法来搜索数组中的项目。 选择哪种方法取决于您的特定用例。
For instance, do you want to get all items in an array that meet a specific condition? Do you want to check if any item meets the condition? Do you want to check if a specific value is in the array? Or do you want to find the index of the value in the array?
例如，您是否要获取数组中满足特定条件的所有项目？ 是否要检查是否满足条件？ 您是否要检查数组中是否有特定值？ 还是要在数组中找到值的索引？
For all these use cases, JavaScript\’s Array.prototype methods have you covered. In this article, we will discuss four methods we can use to search for an item in an array. These methods are:
对于所有这些用例，您都可以了解JavaScript的Array.prototype方法。 在本文中，我们将讨论四种可用于搜索数组中项目的方法。 这些方法是：
- Filter
过滤
- Find
找
- Includes
包括
- IndexOf
指数
Let\’s discuss each of them.
让我们讨论每个。
Array.filter() (Array.filter())
We can use the Array.filter() method to find elements in an array that meet a certain condition. For instance, if we want to get all items in an array of numbers that are greater than 10, we can do this:
我们可以使用Array.filter()方法在满足特定条件的数组中查找元素。 例如，如果我们要获取大于10的数字数组中的所有项目，则可以执行以下操作：
const array = [10, 11, 3, 20, 5];const greaterThanTen = array.filter(element => element > 10);console.log(greaterThanTen) //[11, 20]
The syntax for using the array.filter() method is the following:
使用array.filter()方法的语法如下：
let newArray = array.filter(callback);
where
哪里
-
newArray
is the new array that is returned
newArray
是返回的新数组
-
array
is the array on which the filter method is called
array
是在其上调用filter方法的数组
-
callback
is the callback function that is applied to each element of the array
callback
是应用于数组每个元素的回调函数
If no item in the array meets the condition, an empty array is returned. You can read more about this method here.
如果数组中没有项目符合条件，则返回一个空数组。 您可以在此处阅读有关此方法的更多信息。
There are times when we don\’t need all the elements that meet a certain condition. We just need one element that matches the condition. In that case, you need the find() method.
有时候，我们不需要满足特定条件的所有元素。 我们只需要一个符合条件的元素。 在这种情况下，您需要使用find()方法。
Array.find() (Array.find())
We use the Array.find() method to find the first element that meets a certain condition. Just like the filter method, it takes a callback as an argument and returns the first element that meets the callback condition.
我们使用Array.find()方法查找满足特定条件的第一个元素。 就像filter方法一样，它以回调为参数，并返回满足回调条件的第一个元素。
Let\’s use the find method on the array in our example above.
让我们在上面的示例中对数组使用find方法。
const array = [10, 11, 3, 20, 5];const greaterThanTen = array.find(element => element > 10);console.log(greaterThanTen)//11
The syntax for the array.find() is
array.find()的语法为
let element = array.find(callback);
The callback is the function that is executed on each value in the array and takes three arguments:
回调是在数组中的每个值上执行的函数，带有三个参数：
-
element
– the element being iterated on (required)
element
-该元件上迭代(必需)
-
index
– the index/position of the current element (optional)
index
当前元素的索引/位置(可选)
-
array
– the array that
find
was called on (optional)
array
find
到的数组被调用(可选)
Note, though, that if no item in the array meets the condition, it returns
undefined
.
但是请注意，如果数组中没有项目符合条件，则它将返回
undefined
。
What if, though, you want to check if a certain element is in an array? How do you do this?
但是，如果您想检查某个元素是否在数组中怎么办？ 你怎么做到这一点？
Array.includes() (Array.includes())
The includes() method determines whether an array includes a certain value and returns true or false as appropriate.
includes()方法确定数组是否包含某个值，并在适当时返回true或false。
So in the example above, if we want to check if 20 is one of the elements in the array, we can do this:
因此，在上面的示例中，如果我们要检查20是否为数组中的元素之一，则可以执行以下操作：
const array = [10, 11, 3, 20, 5];const includesTwenty = array.includes(20);console.log(includesTwenty)//true
You\’ll notice a difference between this method and other methods we have considered. This method accepts a value rather than a callback as the argument. Here\’s the syntax for the includes method:
您会注意到此方法与我们考虑的其他方法之间的区别。 此方法接受值而不是回调作为参数。 这是include方法的语法：
const includesValue = array.includes(valueToFind, fromIndex)
Where
哪里
-
valueToFind
is the value you are checking for in the array (required), and
valueToFind
是您要在数组中检查的值(必填)，并且
-
fromIndex
is the index or position in the array that you want to start searching for the element from (optional)
fromIndex
是您要开始从中搜索元素的数组中的索引或位置(可选)
To get the concept of the index, let\’s visit our example again. If we want to check whether the array contains 10 in other positions apart from the first element, we can do this:
要了解索引的概念，让我们再次访问示例。 如果我们要检查数组是否在第一个元素之外的其他位置包含10个，可以这样做：
const array = [10, 11, 3, 20, 5];const includesTenTwice = array.includes(10, 1);console.log(includesTenTwice)//false
Array.indexOf() (Array.indexOf())
The indexOf() method returns the first index at which a given element can be found in an array. It returns -1 if the element does not exist in the array.
indexOf()方法返回可以在数组中找到给定元素的第一个索引。 如果数组中不存在该元素，则返回-1。
Let\’s go back to our example. Let\’s find the index of 3 in the array.
让我们回到我们的例子。 让我们找到数组中的索引3。
const array = [10, 11, 3, 20, 5];const indexOfThree = array.indexOf(3);console.log(indexOfThree)//2
Its syntax is similar to that of the
includes
method.
它的语法类似于
includes
方法。
const indexOfElement = array.indexOf(element, fromIndex)
Where
哪里
-
element
is the element you are checking for in the array (required), and
element
是要在数组中检查的元素(必填)，并且
-
fromIndex
is the index or position in the array that you want to start searching for the element from (optional)
fromIndex
是您要开始从中搜索元素的数组中的索引或位置(可选)
It\’s important to note that both the
includes
and
indexOf
methods use strict equality( \’===\’ ) to search the array. If the values are of different types (for example \’4\’ and 4), they\’ll return
false
and
-1
respectively.
重要的是要注意，
includes
和
indexOf
方法都使用严格相等性(\’===\’)搜索数组。 如果值的类型不同(例如\’4\’和4)，则它们将分别返回
false
和
-1
。
摘要 (Summary)
With these array methods, you don\’t need to use a for loop to search an array. Depending on what you need, you can decide which of the methods is best suited for your use case.
使用这些数组方法，您无需使用for循环即可搜索数组。 根据您的需求，您可以决定哪种方法最适合您的用例。
Here is a summary of when to use each method:
以下是何时使用每种方法的摘要：
-
Use
filter
if you want to find all items in an array that meet a specific condition.
如果要查找数组中满足特定条件的所有项目，请使用
filter
。
-
Use
find
if you want to check if that at least one item meets a specific condition.
如果要检查至少一项是否满足特定条件，请使用
find
。
-
Use
includes
if you want to check if an array contains a particular value.
如果要检查数组是否包含特定值，请使用
includes
。
-
Use
indexOf
if you want to find the index of a particular item in an array.
如果要在数组中查找特定项目的索引，请使用
indexOf
。
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