Set
对象允许你存储任何类型的唯一值,无论是原始值或者是对象引用。
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new Set([iterable]);
一个新的Set
对象。
Set
对象是值的集合,你可以按照插入的顺序迭代它的元素。 Set中的元素只会出现一次,即 Set 中的元素是唯一的。
因为 Set 中的值总是唯一的,所以需要判断两个值是否相等。在ECMAScript规范的早期版本中,这不是基于和===操作符中使用的算法相同的算法。具体来说,对于 Set s, +0 (+0 严格相等于-0)和-0是不同的值。然而,在 ECMAScript 2015规范中这点已被更改。有关详细信息,请参阅浏览器兼容性 表中的“value equality for -0 and 0”。
另外,NaN
和undefined
都可以被存储在Set 中, NaN
之间被视为相同的值(尽管 NaN !== NaN)。
Set.length
length
属性的值为0。get Set[@@species]
Set.prototype
Set
实例所有Set实例继承自 Set.prototype
。
Set.prototype.constructor
Set
。Set.prototype.size
Set
对象的值的个数。Set.prototype.add(value)
Set对象尾部添加一个元素。返回该
Set对象。
Set.prototype.clear()
Set
对象内的所有元素。Set.prototype.delete(value)
移除Set的中与这个值相等的元素,返回Set.prototype.has(value)在这个操作前会返回的值(即如果该元素存在,返回true,否则返回false)。
Set.prototype.has(value)在此后会返回false。
Set.prototype.entries()
返回一个新的迭代器对象,该对象包含Set对象中的
按插入顺序排列的所有元素的值的[value, value]数组。为了使这个方法
和Map对象保持相似,
每个值的键和值相等。Set.prototype.forEach(callbackFn[, thisArg])
thisArg参数,回调中的this会是这个参数。
Set.prototype.has(value)
Set中存在与否。
Set.prototype.keys()
values()
方法相同,返回一个新的迭代器对象,该对象包含Set对象中的
按插入顺序排列的所有元素的值。
Set.prototype.values()
返回一个新的迭代器对象,该对象包含Set对象中的
按插入顺序排列的所有元素的值。
Set.prototype[@@iterator]()
返回一个新的迭代器对象,该对象包含Set对象中的
按插入顺序排列的所有元素的值。
Set
对象let mySet = new Set(); mySet.add(1); // Set(1) {1} mySet.add(5); // Set(2) {1, 5} mySet.add(5); // Set { 1, 5 } mySet.add("some text"); // Set(3) {1, 5, "some text"} var o = {a: 1, b: 2}; mySet.add(o); mySet.add({a: 1, b: 2}); // o 指向的是不同的对象,所以没问题 mySet.has(1); // true mySet.has(3); // false mySet.has(5); // true mySet.has(Math.sqrt(25)); // true mySet.has("Some Text".toLowerCase()); // true mySet.has(o); // true mySet.size; // 5 mySet.delete(5); // true, 从set中移除5 mySet.has(5); // false, 5已经被移除 mySet.size; // 4, 刚刚移除一个值 console.log(mySet); // Set {1, "some text", Object {a: 1, b: 2}, Object {a: 1, b: 2}}
// 迭代整个set // 按顺序输出:1, "some text" for (let item of mySet) console.log(item); // 按顺序输出:1, "some text" for (let item of mySet.keys()) console.log(item); // 按顺序输出:1, "some text" for (let item of mySet.values()) console.log(item); // 按顺序输出:1, "some text" //(键与值相等) for (let [key, value] of mySet.entries()) console.log(key); // 转换Set为Array var myArr = Array.from(mySet); // [1, "some text"] // 如果在HTML文档中工作,也可以: mySet.add(document.body); mySet.has(document.querySelector("body")); // true // Set 和 Array互换 mySet2 = new Set([1,2,3,4]); mySet2.size; // 4 [...mySet2]; // [1,2,3,4] // intersect can be simulated via var intersection = new Set([...set1].filter(x => set2.has(x))); // difference can be simulated via var difference = new Set([...set1].filter(x => !set2.has(x))); // 用forEach迭代 mySet.forEach(function(value) { console.log(value); }); // 1 // 2 // 3 // 4
function isSuperset(set, subset) { for (var elem of subset) { if (!set.has(elem)) { return false; } } return true; } function union(setA, setB) { var _union = new Set(setA); for (var elem of setB) { _union.add(elem); } return _union; } function intersection(setA, setB) { var _intersection = new Set(); for (var elem of setB) { if (setA.has(elem)) { _intersection.add(elem); } } return _intersection; } function difference(setA, setB) { var _difference = new Set(setA); for (var elem of setB) { _difference.delete(elem); } return _difference; } //Examples var setA = new Set([1, 2, 3, 4]), setB = new Set([2, 3]), setC = new Set([3, 4, 5, 6]); isSuperset(setA, setB); // => true union(setA, setC); // => Set [1, 2, 3, 4, 5, 6] intersection(setA, setC); // => Set [3, 4] difference(setA, setC); // => Set [1, 2]
Array
相关var myArray = ["value1", "value2", "value3"]; // 用Set构造器将Array转换为Set var mySet = new Set(myArray); mySet.has("value1"); // returns true // 用...(展开操作符)操作符将Set转换为Array console.log([...mySet]); // 与myArray完全一致
String
相关var text = 'Indiana'; var mySet = new Set(text); // Set {'I', 'n', 'd', 'i', 'a'} mySet.size; // 5
// Use to remove duplicate elements from the array const numbers = [2,3,4,4,2,3,3,4,4,5,5,6,6,7,5,32,3,4,5] console.log([...new Set(numbers)]) // [2, 3, 4, 5, 6, 7, 32]
规范 | 状态 | 备注 |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) Set |
Standard | 初始定义 |
ECMAScript Latest Draft (ECMA-262) Set |
Draft |
The compatibility table on 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.
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Set | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 13 | IE Full support 11 | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 14 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs
Full support
0.12
|
new Set(iterable) | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 13 | IE No support No | Opera Full support 25 | Safari Full support 9 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 14 | Opera Android Full support 25 | Safari iOS Full support 9 | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |
new Set(null) | Chrome Full support Yes | Edge Full support 12 | Firefox Full support 37 | IE Full support 11 | Opera Full support Yes | Safari Full support 9 | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support 12 | Firefox Android Full support 37 | Opera Android Full support Yes | Safari iOS Full support 9 | Samsung Internet Android Full support Yes | nodejs
Full support
0.12
|
Set() without new throws | Chrome Full support Yes | Edge Full support 12 | Firefox Full support 42 | IE Full support 11 | Opera Full support Yes | Safari Full support 9 | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support 12 | Firefox Android Full support 42 | Opera Android Full support Yes | Safari iOS Full support 9 | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |
Key equality for -0 and 0 | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 29 | IE No support No | Opera Full support 25 | Safari Full support 9 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 29 | Opera Android Full support 25 | Safari iOS Full support 9 | Samsung Internet Android Full support Yes | nodejs Full support 4.0.0 |
add | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 13 | IE
Partial support
11
| Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 14 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support Yes |
clear | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 19 | IE Full support 11 | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 19 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |
delete | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 13 | IE Full support 11 | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 14 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs
Full support
0.12
|
entries | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 24 | IE No support No | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 24 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |
forEach | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 25 | IE Full support 11 | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 25 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |
has | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 13 | IE Full support 11 | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 14 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support Yes |
prototype | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 13 | IE Full support 11 | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 14 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support Yes |
size | Chrome Full support 38 | Edge Full support 12 | Firefox
Full support
19
| IE Full support 11 | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android
Full support
19
| Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |
values | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 24 | IE No support No | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 24 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |
@@iterator | Chrome Full support Yes | Edge Full support Yes | Firefox
Full support
36
| IE No support No | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android
Full support
36
| Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |
@@species | Chrome Full support 51 | Edge Full support 13 | Firefox Full support 41 | IE No support No | Opera Full support 38 | Safari Full support 10 | WebView Android Full support 51 | Chrome Android Full support 51 | Edge Mobile Full support 13 | Firefox Android Full support 41 | Opera Android Full support 41 | Safari iOS Full support 10 | Samsung Internet Android Full support 5.0 | nodejs
Full support
6.5.0
|