function Set() {

let items = {};

this.has = function (value) {

return items.hasOwnProperty(value);

};

this.add = function (value) {

if (!this.has(value)) {

items[value] = value;

return true;

}

return false;

};

this.remove = function (value) {

if (this.has(value)) {

delete items[value];

return true;

}

return false;

};

this.print = function () {

console.log(items);

}

this.clear = function() {

items = {};

};

this.size = function () {

return Object.keys(items).length;

};

this.value = function () {

let values = [];

for (let value in items) {

values.push(value);

}

return values;

};

this.union = function (otherSet) { //并集

let unionSet = new Set();

let values = this.value();

for (var i = 0; i < values.length; i++) {

unionSet.add(values[i]);

}

values = otherSet.value();

for (var i = 0; i < values.length; i++) {

unionSet.add(values[i]);

}

return unionSet;

};

this.intersection = function (otherSet) { //交集

let intersectionSet = new Set();

let values = this.value();

for (var i = 0; i < values.length; i++) {

if (otherSet.has(values[i])) {

intersectionSet.add(values[i]);

}

}

return intersectionSet;

};

this.difference = function (otherSet) { //差集

let differenceSet = new Set();

let values = this.value();

for (var i = 0; i < values.length; i++) {

if (!otherSet.has(values[i])) {

differenceSet.add(values[i]);

}

}

return differenceSet;

};

this.subset = function(otherSet) { //子集

if (this.size() > otherSet.size()) {

return false;

} else {

let values = this.value();

for (let i = 0; i < values.length; i++) {

if (!otherSet.has(values[i])) {

return false;

}

}

return true;

}

};

}

let setA = new Set();

setA.add('Cyclone');

let setB = new Set();

setB.add('Cyclone');

setB.add('Luna');

setB.add('Metal');

console.log(setA.subset(setB));