---
id: 587d8254367417b2b2512c6e
title: Perform a Difference on Two Sets of Data
challengeType: 1
videoUrl: ''
localeTitle: 对两组数据执行差异
---

## Description
<section id="description">在本练习中，我们将对两组数据进行区分。我们将在我们的<code>Set</code>数据结构上创建一个名为<code>difference</code> 。集合的差异应比较两组并返回第一组中不存在的项目。此方法应将另一个<code>Set</code>作为参数，并返回两个集的<code>difference</code> 。例如，如果<code>setA = [&#39;a&#39;,&#39;b&#39;,&#39;c&#39;]</code>和<code>setB = [&#39;a&#39;,&#39;b&#39;,&#39;d&#39;,&#39;e&#39;]</code> ，则setA和setB的差异为： <code>setA.difference(setB) = [&#39;c&#39;]</code> 。 </section>

## Instructions
<section id="instructions">
</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: 你的<code>Set</code>类应该有一个<code>difference</code>方法。
    testString: 'assert(function(){var test = new Set(); return (typeof test.difference === "function")}, "Your <code>Set</code> class should have a <code>difference</code> method.");'
  - text: 收回了适当的收藏
    testString: 'assert(function(){var setA = new Set(); var setB = new Set(); setA.add("a"); setA.add("b"); setA.add("c"); setB.add("c"); setB.add("d"); var differenceSetAB = setA.difference(setB); return (differenceSetAB.size() === 2) && (differenceSetAB.values() === [ "a", "b" ])}, "The proper collection was returned");'

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
function Set() {
    // the var collection will hold the set
    var collection = [];
    // this method will check for the presence of an element and return true or false
    this.has = function(element) {
        return (collection.indexOf(element) !== -1);
    };
    // this method will return all the values in the set
    this.values = function() {
        return collection;
    };
    // this method will add an element to the set
    this.add = function(element) {
        if(!this.has(element)){
            collection.push(element);
            return true;
        }
        return false;
    };
    // this method will remove an element from a set
    this.remove = function(element) {
        if(this.has(element)){
           var index = collection.indexOf(element);
            collection.splice(index,1);
            return true;
        }
        return false;
    };
    // this method will return the size of the collection
    this.size = function() {
        return collection.length;
    };
    // this method will return the union of two sets
    this.union = function(otherSet) {
        var unionSet = new Set();
        var firstSet = this.values();
        var secondSet = otherSet.values();
        firstSet.forEach(function(e){
            unionSet.add(e);
        });
        secondSet.forEach(function(e){
            unionSet.add(e);
        });
        return unionSet;
    };
    // this method will return the intersection of two sets as a new set
    this.intersection = function(otherSet) {
        var intersectionSet = new Set();
        var firstSet = this.values();
        firstSet.forEach(function(e){
            if(otherSet.has(e)){
                intersectionSet.add(e);
            }
        });
        return intersectionSet;
    };
    // change code below this line
    // change code above this line
}

```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```
</section>