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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

句法

arr.includes(valueToFind[, fromIndex])
					

参数

valueToFind

The value to search for.

注意： When comparing strings and characters, includes() is case-sensitive .

fromIndex 可选

The position in this array at which to begin searching for valueToFind .

The first element to be searched is found at fromIndex for positive values of fromIndex , or at arr .length + fromIndex for negative values of fromIndex (using the absolute value of fromIndex as the number of elements from the end of the array at which to start the search).

Defaults to 0 .

返回值

A 布尔 which is true if the value valueToFind is found within the array (or the part of the array indicated by the index fromIndex , if specified).

Values of zero are all considered to be equal, regardless of sign. (That is, -0 is considered to be equal to both 0 and +0 ), but false is not considered to be the same as 0 .

注意： Technically speaking, includes() 使用 sameValueZero algorithm to determine whether the given element is found.

范例

[1, 2, 3].includes(2)      // true
[1, 2, 3].includes(4)      // false
[1, 2, 3].includes(3, 3)   // false
[1, 2, 3].includes(3, -1)  // true
[1, 2, NaN].includes(NaN)  // true
					

fromIndex is greater than or equal to the array length

若 fromIndex is greater than or equal to the length of the array, false is returned. The array will not be searched.

let arr = ['a', 'b', 'c']
arr.includes('c', 3)    // false
arr.includes('c', 100)  // false
					

Computed index is less than 0

若 fromIndex is negative, the computed index is calculated to be used as a position in the array at which to begin searching for valueToFind . If the computed index is less or equal than -1 * arr .length , the entire array will be searched.

// array length is 3
// fromIndex is -100
// computed index is 3 + (-100) = -97
let arr = ['a', 'b', 'c']
arr.includes('a', -100) // true
arr.includes('b', -100) // true
arr.includes('c', -100) // true
arr.includes('a', -2)   // false
					

includes() used as a generic method

includes() method is intentionally generic. It does not require this value to be an Array object, so it can be applied to other kinds of objects (e.g. array-like objects).

The example below illustrates includes() method called on the function's arguments 对象。

(function() {
  console.log(Array.prototype.includes.call(arguments, 'a'))  // true
  console.log(Array.prototype.includes.call(arguments, 'd'))  // false
})('a','b','c')
					

Please do not add polyfills on reference articles. For more details and discussion, see https://discourse.mozilla.org/t/mdn-rfc-001-mdn-wiki-pages-shouldnt-be-a-distributor-of-polyfills/24500

规范

规范
ECMAScript (ECMA-262) The definition of 'Array.prototype.includes' in that specification.

浏览器兼容性

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
includes	Chrome 47	Edge 14	Firefox 43	IE No	Opera 34	Safari 9	WebView Android 47	Chrome Android 47	Firefox Android 43	Opera Android 34	Safari iOS 9	Samsung Internet Android 5.0	nodejs 6.0.0 6.0.0 5.0.0 Disabled Disabled From version 5.0.0: this feature is behind the --harmony runtime flag.

图例

完整支持

完整支持

不支持

不支持

用户必须明确启用此特征。

用户必须明确启用此特征。

另请参阅

• TypedArray.prototype.includes()
• String.prototype.includes()
• Array.prototype.indexOf()
• Array.prototype.find()
• Array.prototype.findIndex()

元数据

• 最后修改： Jul 25, 2020

相关话题

1. 标准内置对象
2. Array
3. 特性
   1. Array.prototype.length
   2. Array.prototype[@@unscopables]
4. 方法
   1. Array.from()
   2. Array.isArray()
   3. Array.of()
   4. Array.prototype.concat()
   5. Array.prototype.copyWithin()
   6. Array.prototype.entries()
   7. Array.prototype.every()
   8. Array.prototype.fill()
   9. Array.prototype.filter()
   10. Array.prototype.find()
   11. Array.prototype.findIndex()
   12. Array.prototype.flat()
   13. Array.prototype.flatMap()
   14. Array.prototype.forEach()
   15. Array.prototype.includes()
   16. Array.prototype.indexOf()
   17. Array.prototype.join()
   18. Array.prototype.keys()
   19. Array.prototype.lastIndexOf()
   20. Array.prototype.map()
   21. Array.prototype.pop()
   22. Array.prototype.push()
   23. Array.prototype.reduce()
   24. Array.prototype.reduceRight()
   25. Array.prototype.reverse()
   26. Array.prototype.shift()
   27. Array.prototype.slice()
   28. Array.prototype.some()
   29. Array.prototype.sort()
   30. Array.prototype.splice()
   31. Array.prototype.toLocaleString()
   32. Array.prototype.toSource()
   33. Array.prototype.toString()
   34. Array.prototype.unshift()
   35. Array.prototype.values()
   36. Array.prototype[@@iterator]()
   37. get Array[@@species]
5. 继承：
6. Function
7. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
9. Object
10. 特性
    1. Object.prototype.__proto__
    2. Object.prototype.constructor
11. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()