<!DOCTYPE html>
<html>
<head>
<title>集合</title>
<meta charset="utf-8">
<script type="text/javascript">
function Set(){ let items = {}; // add：添加一个新的项
this.add = function(value){
if(!this.has(value)){
// 添加一个值的时候，把它同时作为键和值保存，有利于查找这个值
items[value] = value;
return true;
}
return false;
}; // delete：删除值
this.delete = function(value){
if(this.has(value)){
delete items[value];
return true;
}
return false;
}; // has：如果值在集合中返回true，否则返回false
this.has = function(value){
return items.hasOwnProperty(value);
}; // clear：移除集合中的所有项
this.clear = function(){
items = {};
}; // size：返回集合中所包含的元素数量，与数组的length属性类似
this.size = function(){
return Object.keys(items).length;
}; // sizeLegacy：跨浏览器兼容返回集合元素数量
this.sizeLegacy = function(){
let count = 0;
for(let key in items){
if(items.hasOwnPrototype(key)){
++count;
}
}
return count;
}; // values：返回一个包含集合中所有数据的数组
this.values = function(){
let values = [];
for(let i=0, keys = Object.keys(items); i<keys.length; i++){
values.push(items[keys[i]]);
}
return values;
}; // valuesLegacy：跨浏览器兼容
this.valuesLegacy = function(){
let values = [];
for(let key in items){
if(items.hasOwnPrototype(key)){
values.push(items[key]);
}
}
return values;
}; // getItems
this.getItems = function(){
return items;
}; // union：并集
this.union = function(otherSet){
let unionSet = new Set(); let values = this.values();
for(let i=0; i<values.length; i++){
unionSet.add(values[i]);
} values = otherSet.values();
for(let i=0; i<values.length; i++){
unionSet.add(values[i]);
}
return unionSet;
}; // intersection：交集
this.intersection = function(otherSet){
let intersectionSet = new Set(); let values = this.values();
for(let i=0; i<values.length; i++){
if(otherSet.has(values[i])){
intersectionSet.add(values[i]);
}
}
return intersectionSet;
}; //difference：差集
this.difference = function(otherSet){
let differenceSet = new Set();
let values = this.values();
for(let i=0; i<values.length; i++){
if(!otherSet.has(values[i])){
differenceSet.add(values[i]);
}
}
return differenceSet;
}; // subset：子集
this.subset = function(otherSet){
if(this.size() > otherSet.size()){
return false;
}
else{
let values = this.values();
for(let i=0; i<values.length; i++){
if(!otherSet.has(values[i])){
return false;
}
}
}
return true;
} } // Set的使用
var set1 = new Set();
set1.add(1);
set1.add(2);
set1.add(3); var set2 = new Set();
set2.add(1);
set2.add(2);
set2.add(3);
set2.add(4);
set2.add(5); var set3 = new Set();
set3.add("a");
set3.add("b");
set3.add("c");
set3.add("d"); // 打印集合大小
console.log(set1.size()); //3
console.log(set2.size()); //5
console.log(set3.size()); //4 //打印集合元素的数组形式
console.log(set1.values()); //[1,2,3]
console.log(set2.values()); //[1,2,3,4,5]
console.log(set3.values()); //["a", "b", "c", "d"] // 求set1和set2的并集
let set12 = set1.union(set2);
console.log(set12.values()); //[1,2,3,4,5] // 求set1和set2的交集
let _set12 = set1.intersection(set2);
console.log(_set12.values()); //[1,2,3] // 求set1和set2的差集
let set2_1 = set2.difference(set1);
console.log(set2_1.values()); //[4,5] // 判断set1是否为set2的子集
console.log(set1.subset(set2)); //true // 判断set3是否为set2的子集
console.log(set3.subset(set2)); //false
</script>
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<body> </body>
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