ES6的JavaScript数据结构实现之集合

目的：ES6标准下的JS数据结构的一些实现代码。（作为记录和启发）

内容：集合。（未完成，待继续）

所有源码在我的Github上（如果觉得不错记得给星鼓励我哦）：ES6的JavaScript数据结构实现之集合

注：Set类在ES6中已经提供了原生的Set结构。

一、基础数据结构

1、集合（非ES6自带的原生Set）

class Set {
  constructor() {
    this.items = {};
  }
  has(element) {
    return Object.prototype.hasOwnProperty.call(this.items, element);
  }
  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;
  }
  clear() {
    this.items = {};
  }
  size() {
    return Object.keys(this.items).length;
  }
  values() {
    return Object.values(this.items);
  }
  union(otherSet) {
    const unionSet = new Set();
    this.values().forEach(value => unionSet.add(value));
    otherSet.values().forEach(value => unionSet.add(value));
    return unionSet;
  }
  intersection(otherSet) {
    const intersectionSet = new Set();
    const values = this.values();
    const otherValues = otherSet.values();
    let biggerSet = values;
    let smallerSet = otherValues;
    if (otherValues.length - values.length > 0) {
      biggerSet = otherValues;
      smallerSet = values;
    }
    smallerSet.forEach(value => {
      if (biggerSet.includes(value)) {
        intersectionSet.add(value);
      }
    });
    return intersectionSet;
  }
  difference(otherSet) {
    const differenceSet = new Set();
    this.values().forEach(value => {
      if (!otherSet.has(value)) {
        differenceSet.add(value);
      }
    });
    return differenceSet;
  }
  isSubsetOf(otherSet) {
    if (this.size() > otherSet.size()) {
      return false;
    }
    let isSubset = true;
    this.values().every(values => {
      if(!otherSet.has(values)) {
        isSubset = false;
        return false; 
      }
      return true;
    });
    return isSubset;
  }

  isEmpty() {
    return this.size() === 0;
  }
  toString() {
    if (this.isEmpty()) {
      return '';
    }
    const values = this.values();
    let objString = `${values[0]}`;
    for (let i = 1; i < values.length; i++) {
      objString = `${objString},${values[i].toString()}`;
    }
    return objString;
  }


}

const set = new Set();
set.add(1);
set.add(2);
set.add(3);
console.log(set);
set.delete(1);
console.log(set);
console.log(set.size());
console.log(set.values());
const setB = new Set();
setB.add(3);
setB.add(5);
setB.add(6);
console.log(setB);
console.log(set.union(setB));
console.log(set.intersection(setB));
console.log(set.difference(setB));
console.log(setB.difference(set));
console.log(set.isSubsetOf(setB));
const setC = new Set();
setC.add(5);
setC.add(6);
console.log(setC.isSubsetOf(setB));

2、ES6原生的Set类。（ES6中的原生的Set没有交、并、差运算，需要我们自己写。同时，我们可以结合使用扩展运算符，把集合转为为数组，再对数组进行运算，再转回集合。）

const set = new Set();

set.add(1);
console.log(set.values()); // outputs @Iterator
console.log(set.has(1)); // outputs true
console.log(set.size); // outputs 1

set.add(2);
console.log(set.values()); // outputs [1, 2]
console.log(set.has(2)); // true
console.log(set.size); // 2

set.delete(1);
console.log(set.values()); // outputs [2]

set.delete(2);
console.log(set.values()); // outputs []

const setA = new Set();
setA.add(1);
setA.add(2);
setA.add(3);

const setB = new Set();
setB.add(2);
setB.add(3);
setB.add(4);

// --------- Union ----------
const union = (set1, set2) => {
  const unionAb = new Set();
  set1.forEach(value => unionAb.add(value));
  set2.forEach(value => unionAb.add(value));
  return unionAb;
};
console.log(union(setA, setB));

console.log(new Set([...setA, ...setB]));

// --------- Intersection ----------
const intersection = (set1, set2) => {
  const intersectionSet = new Set();
  set1.forEach(value => {
    if (set2.has(value)) {
      intersectionSet.add(value);
    }
  });
  return intersectionSet;
};
console.log(intersection(setA, setB));

console.log(new Set([...setA].filter(x => setB.has(x))));

// alternative - works on FF only
// console.log(new Set([x for (x of setA) if (setB.has(x))]));

// --------- Difference ----------
const difference = (set1, set2) => {
  const differenceSet = new Set();
  set1.forEach(value => {
    if (!set2.has(value)) {
      differenceSet.add(value);
    }
  });
  return differenceSet;
};
console.log(difference(setA, setB));

console.log(new Set([...setA].filter(x => !setB.has(x))));

// alternative  - works on FF only
// console.log(new Set([x for (x of setA) if (!setB.has(x))]));