---
id: 587d8254367417b2b2512c6f
title: 对两组数据执行子集检查
challengeType: 1
videoUrl: ''
dashedName: perform-a-subset-check-on-two-sets-of-data
---

# --description--

在本练习中，我们将对2组数据执行子集测试。我们将在我们的`Set`数据结构上创建一个名为`subset` 。这将比较第一组与第二组，如果第一组完全包含在第二组中，则它将返回true。例如，如果`setA = ['a','b']`和`setB = ['a','b','c','d']` ，则setA和setB的子集为： `setA.subset(setB)`应该是`true` 。

# --hints--

你的`Set`类应该有一个`union`方法。

```js
assert(
  (function () {
    var test = new Set();
    return typeof test.subset === 'function';
  })()
);
```

第一个Set（）包含在第二个Set中

```js
assert(
  (function () {
    var setA = new Set();
    var setB = new Set();
    setA.add('a');
    setB.add('b');
    setB.add('c');
    setB.add('a');
    setB.add('d');
    var subsetSetAB = setA.subset(setB);
    return subsetSetAB === true;
  })()
);
```

`["a", "b"].subset(["a", "b", "c", "d"])`应该返回`true` “）

```js
assert(
  (function () {
    var setA = new Set();
    var setB = new Set();
    setA.add('a');
    setA.add('b');
    setB.add('a');
    setB.add('b');
    setB.add('c');
    setB.add('d');
    var subsetSetAB = setA.subset(setB);
    return subsetSetAB === true;
  })()
);
```

`["a", "b", "c"].subset(["a", "b"])`应返回`false` “）

```js
assert(
  (function () {
    var setA = new Set();
    var setB = new Set();
    setA.add('a');
    setA.add('b');
    setA.add('c');
    setB.add('a');
    setB.add('b');
    var subsetSetAB = setA.subset(setB);
    return subsetSetAB === false;
  })()
);
```

`[].subset([])`应该返回`true`

```js
assert(
  (function () {
    var setA = new Set();
    var setB = new Set();
    var subsetSetAB = setA.subset(setB);
    return subsetSetAB === true;
  })()
);
```

`["a", "b"].subset(["c", "d"])`应返回`false` “）

```js
assert(
  (function () {
    var setA = new Set();
    var setB = new Set();
    setA.add('a');
    setA.add('b');
    setB.add('c');
    setB.add('d');
    var subsetSetAB = setA.subset(setB);
    return subsetSetAB === false;
  })()
);
```

# --seed--

## --seed-contents--

```js
class Set {
  constructor() {
    // This will hold the set
    this.dictionary = {};
    this.length = 0;
  }
  // This method will check for the presence of an element and return true or false
  has(element) {
    return this.dictionary[element] !== undefined;
  }
  // This method will return all the values in the set
  values() {
    return Object.keys(this.dictionary);
  }
  // This method will add an element to the set
  add(element) {
    if (!this.has(element)) {
      this.dictionary[element] = true;
      this.length++;
      return true;
    }

    return false;
  }
  // This method will remove an element from a set
  remove(element) {
    if (this.has(element)) {
      delete this.dictionary[element];
      this.length--;
      return true;
    }

    return false;
  }
  // This method will return the size of the set
  size() {
    return this.length;
  }
  // This is our union method 
  union(set) {
    const newSet = new Set();
    this.values().forEach(value => {
      newSet.add(value);
    })
    set.values().forEach(value => {
      newSet.add(value);
    })

    return newSet;
  }
  // This is our intersection method
  intersection(set) {
    const newSet = new Set();

    let largeSet;
    let smallSet;
    if (this.dictionary.length > set.length) {
      largeSet = this;
      smallSet = set;
    } else {
      largeSet = set;
      smallSet = this;
    }

    smallSet.values().forEach(value => {
      if (largeSet.dictionary[value]) {
        newSet.add(value);
      }
    })

    return newSet;
  }

  difference(set) {
    const newSet = new Set();

    this.values().forEach(value => {
      if (!set.dictionary[value]) {
        newSet.add(value);
      }
    })

    return newSet;
  }
  // Only change code below this line
  
  // Only change code above this line
}
```

# --solutions--

```js
class Set {
  constructor() {
    this.dictionary = {};
    this.length = 0;
  }

  has(element) {
    return this.dictionary[element] !== undefined;
  }

  values() {
    return Object.keys(this.dictionary);
  }

  add(element) {
    if (!this.has(element)) {
      this.dictionary[element] = true;
      this.length++;
      return true;
    }

    return false;
  }

  remove(element) {
    if (this.has(element)) {
      delete this.dictionary[element];
      this.length--;
      return true;
    }

    return false;
  }

  size() {
    return this.length;
  }

  union(set) {
    const newSet = new Set();
    this.values().forEach(value => {
      newSet.add(value);
    })
    set.values().forEach(value => {
      newSet.add(value);
    })

    return newSet;
  }

  intersection(set) {
    const newSet = new Set();

    let largeSet;
    let smallSet;
    if (this.dictionary.length > set.length) {
      largeSet = this;
      smallSet = set;
    } else {
      largeSet = set;
      smallSet = this;
    }

    smallSet.values().forEach(value => {
      if (largeSet.dictionary[value]) {
        newSet.add(value);
      }
    })

    return newSet;
  }  

  difference(set) {
    const newSet = new Set();

    this.values().forEach(value => {
      if (!set.dictionary[value]) {
        newSet.add(value);
      }
    })

    return newSet;
  }

  isSubsetOf(set) {
    for(const value of this.values()){
      if(!set.dictionary[value]) return false;
    }
    return true
  }
}
```