includes()
方法用来判断当前数组是否包含某指定的值,如果是,则返回 true
,否则返回 false
。
语法
var boolean = array.includes(searchElement[, fromIndex])
参数
searchElement
- 需要查找的元素值。
fromIndex
- 可选参数。从该索引处开始查找
searchElement
,默认为 0。
返回值
一个 Boolean
。
示例
[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
Polyfill
if (!Array.prototype.includes) { Array.prototype.includes = function(searchElement /*, fromIndex*/ ) { 'use strict'; if (this == null) { throw new TypeError('Array.prototype.includes called on null or undefined'); } var O = Object(this); var len = parseInt(O.length, 10) || 0; if (len === 0) { return false; } var n = parseInt(arguments[1], 10) || 0; var k; if (n >= 0) { k = n; } else { k = len + n; if (k < 0) {k = 0;} } var currentElement; while (k < len) { currentElement = O[k]; if (searchElement === currentElement || (searchElement !== searchElement && currentElement !== currentElement)) { return true; } k++; } return false; }; }
规范
Specification | Status | Comment |
---|---|---|
ECMAScript 2016 (ECMA-262) Array.prototype.includes |
Standard | Initial definition. |
ECMAScript 2017 Draft (ECMA-262) Array.prototype.includes |
Draft |
浏览器兼容性
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 47 | Nightly build | 未实现 | 34 | 9 |
Feature | Android | Android Webview | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|---|
Basic support | 未实现 | 47 | 47 | 43 | 未实现 | 34 | 9 |