JavaScript - 集合

基于 ES2015 创建集合类

class Set {
  constructor() {
    this.items = {};
  }
  add(element) {
    if (!this.has(element)) {
      this.items[element] = element;
      return true;
    }
    return false;
  }
  delete(element) {
    if (this.has(element)) {
      delete this.items[element];
      return true;
    }
    return false;
  }
  has(element) {
    // return element in this.items;
    return Object.prototype.hasOwnProperty.call(this.items, element);
  }
  clear() {}
  size() {
    let count = 0;
    for (let key in this.items) {
      if (this.items.hasOwnProperty(key)) {
        count += 1;
      }
    }
    return count;
  }
  values() {
    let values = [];
    for (let key in this.items) {
      if (this.items.hasOwnProperty(key)) {
        values.push(key);
      }
    }
    return values;
  }
  // 并集
  union(otherSet) {
    const unionSet = new Set();
    let values = this.values();
    for (let i = 0; i < values.length; i += 1) {
      unionSet.add(values[i]);
    }
    values = otherSet.values;
    for (let i = 0; i < values.length; i += 1) {
      unionSet.add(values[i]);
    }
    return unionSet;
  }
  // 交集
  intersection(otherSet) {
    const intersectionSet = new Set();
    const values = this.values();
    for (let i = 0; i < values.length; i += 1) {
      if (otherSet.has(values[i])) {
        intersectionSet.add(values[i]);
      }
    }
    return intersectionSet;
  }
  // 差集
  difference(otherSet) {
    const differenceSet = new Set();
    this.values().forEach((value) => {
      if (!otherSet.has(value)) {
        differenceSet.add(value);
      }
    });
    return differenceSet;
  }
  // 子集
  isSubsetOf(otherSet) {
    if (this.size() > otherSet.size()) {
      return false;
    }
    let isSubset = true;
    this.values().every((value) => {
      if (!otherSet.has(value)) {
        isSubset = false;
        return false;
      }
      return true;
    });
    return isSubset;
  }
}