JavaScript --- Set 集合结构详解

 1 const set1 = new Set([1, 2, 3, 4, 5]);
 2 
 3 console.log(set1.has(1));
 4 // expected output: true
 5 
 6 console.log(set1.has(5));
 7 // expected output: true
 8 
 9 console.log(set1.has(6));
10 // expected output: false

 1 let mySet = new Set();
 2 
 3 mySet.add(1); // Set(1) {1}
 4 mySet.add(5); // Set(2) {1, 5}
 5 mySet.add(5); // Set { 1, 5 }
 6 mySet.add("some text"); // Set(3) {1, 5, "some text"}
 7 var o = {a: 1, b: 2};
 8 mySet.add(o);
 9 
10 mySet.add({a: 1, b: 2}); // o 指向的是不同的对象，所以没问题
11 
12 mySet.has(1); // true
13 mySet.has(3); // false
14 mySet.has(5);              // true
15 mySet.has(Math.sqrt(25));  // true
16 mySet.has("Some Text".toLowerCase()); // true
17 mySet.has(o); // true
18 
19 mySet.size; // 5
20 
21 mySet.delete(5);  // true,  从set中移除5
22 mySet.has(5);     // false, 5已经被移除
23 
24 mySet.size; // 4, 刚刚移除一个值
25 console.log(mySet); // Set {1, "some text", Object {a: 1, b: 2}, Object {a: 1, b: 2}}

 1 // 迭代整个set
 2 // 按顺序输出：1, "some text" 
 3 for (let item of mySet) console.log(item);
 4 
 5 // 按顺序输出：1, "some text" 
 6 for (let item of mySet.keys()) console.log(item);
 7  
 8 // 按顺序输出：1, "some text" 
 9 for (let item of mySet.values()) console.log(item);
10 
11 // 按顺序输出：1, "some text" 
12 //(键与值相等)
13 for (let [key, value] of mySet.entries()) console.log(key);
14 
15 // 转换Set为Array (with Array comprehensions)
16 var myArr = [v for (v of mySet)]; // [1, "some text"]
17 // 替代方案(with Array.from)
18 var myArr = Array.from(mySet); // [1, "some text"]
19 
20 // 如果在HTML文档中工作，也可以：
21 mySet.add(document.body);
22 mySet.has(document.querySelector("body")); // true
23 
24 // Set 和 Array互换
25 mySet2 = new Set([1,2,3,4]);
26 mySet2.size; // 4
27 [...mySet2]; // [1,2,3,4]
28 
29 // intersect can be simulated via 
30 var intersection = new Set([...set1].filter(x => set2.has(x)));
31 
32 // difference can be simulated via
33 var difference = new Set([...set1].filter(x => !set2.has(x)));
34 
35 // 用forEach迭代
36 mySet.forEach(function(value) {
37   console.log(value);
38 });
39 
40 // 1
41 // 2
42 // 3
43 // 4

1 var myArray = ["value1", "value2", "value3"];
2 
3 // 用Set构造器将Array转换为Set
4 var mySet = new Set(myArray);
5 
6 mySet.has("value1"); // returns true
7 
8 // 用...(展开操作符)操作符将Set转换为Array
9 console.log([...mySet]); // 与myArray完全一致

1 var text = 'Indiana';
2 
3 var mySet = new Set(text);  // Set {'I', 'n', 'd', 'i', 'a'}
4 mySet.size;  // 5