path: root/files/de/web/javascript/reference/global_objects/set/index.html

---
title: Set
slug: Web/JavaScript/Reference/Global_Objects/Set
tags:
  - ECMAScript6
  - Global Objects
  - JavaScript
  - Referenz
  - set
translation_of: Web/JavaScript/Reference/Global_Objects/Set
---
<div>{{JSRef}}</div>

<p>Ein <strong><code>Set</code></strong>-Objekt speichert <em>eindeutige</em> Werte jedes beliebigen Typs, egal ob es sich dabei um {{Glossary("Primitive", "primitive Werte")}} oder Objektreferenzen handelt.</p>

<div>{{EmbedInteractiveExample("pages/js/set-prototype-constructor.html")}}</div>



<h2 id="Syntax">Syntax</h2>

<pre class="syntaxbox notranslate">new Set([iterable]);</pre>

<h3 id="Parameter">Parameter</h3>

<dl>
 <dt>iterable</dt>
 <dd>Ein <a href="/de/docs/Web/JavaScript/Reference/Statements/for...of">iterierbares Objekt</a>, dessen Elemente zum neuen <code>Set</code> hinzugefügt werden sollen.<br>
 Ist dieser Parameter nicht angegeben oder <code>null</code>, wird ein leeres <code>Set</code> erzeugt.</dd>
</dl>

<h3 id="Rückgabewert">Rückgabewert</h3>

<p>Ein neues <code>Set</code> Objekt.</p>

<h2 id="Beschreibung">Beschreibung</h2>

<p><code>Set</code> Objekte sind Sammlungen von Werten. Man kann über die Elemente iterieren; sie werden in der Reihenfolge ihres Hinzufügens gespeichert. Jeder Wert ist <strong>nur einmal vorhanden</strong>; er ist im <code>Set</code> eindeutig.</p>

<h3 id="Gleichheit">Gleichheit</h3>

<p>Da jeder Wert innerhalb eines <code>Set</code>s eindeutig sein muss, werden alle Werte auf Gleichheit überprüft. In einer früheren Version der ECMAScript Spezifikation verhielt sich der Algorithmus dafür anders als der für den <code>===</code> Operator. Insbesondere waren für <code>Set</code>s <code>+0</code> und <code>-0</code> verschiedene Werte (obwohl sie streng gleich sind). In der ECMAScript 2015 Spezifikation wurde das geändert, so dass <code>+0</code> und <code>-0</code> jetzt jeweils als gleicher Wert gelten. Siehe auch den Eintrag "Key equality for -0 and 0" in der Übersicht zur <a href="#browserkompatibilität">Browserkompatibilität</a>.</p>

<p>{{jsxref("NaN")}} und {{jsxref("undefined")}} können ebenfalls in einem Set gespeichert werden. Dabei werden alle <code>NaN</code> Werte gleichgesetzt, d.h. <code>NaN</code> gilt gleich <code>NaN</code> (auch wenn <code>NaN !== NaN</code>).</p>

<h2 id="Eigenschaften">Eigenschaften</h2>

<dl>
 <dt><code>Set.length</code></dt>
 <dd>Der Wert der Eigenschaft <code>length</code> ist immer 0.<br>
 Die Anzahl der Elemente eines Sets befindet sich in {{jsxref("Set.prototype.size")}}.</dd>
 <dt>{{jsxref("Set.@@species", "get Set[@@species]")}}</dt>
 <dd>Die Konstruktorfunktion, um abgeleitete Objekte zu erzeugen.</dd>
 <dt>{{jsxref("Set.prototype")}}</dt>
 <dd>Prototyp für den <code>Set</code> Konstruktor. Ermöglicht das Hinzufügen von Eigenschaften zu allen <code>Set</code> Objekten.</dd>
</dl>

<h2 id="Set_Instanzen"><code>Set</code> Instanzen</h2>

<p>Alle <code>Set</code> Instanzen erben von {{jsxref("Set.prototype")}}.</p>

<h3 id="Eigenschaften_2">Eigenschaften</h3>

<p>{{page('en-US/Web/JavaScript/Reference/Global_Objects/Set/prototype','Properties')}}</p>

<h3 id="Methoden">Methoden</h3>

<p>{{page('en-US/Web/JavaScript/Reference/Global_Objects/Set/prototype','Methods')}}</p>

<h2 id="Beispiele">Beispiele</h2>

<h3 id="Verwenden_eines_Set_Objekts">Verwenden eines <code>Set</code> Objekts</h3>

<pre class="brush: js notranslate">var mySet = new Set();

mySet.add(1);
mySet.add(5);
mySet.add("some text");
var o = {a: 1, b: 2};
mySet.add(o);

mySet.has(1); // true
mySet.has(3); // false, 3 has not been added to the set
mySet.has(5);              // true
mySet.has(Math.sqrt(25));  // true
mySet.has("Some Text".toLowerCase()); // true
mySet.has(o); // true

mySet.size; // 4

mySet.delete(5); // removes 5 from the set
mySet.has(5);    // false, 5 has been removed

mySet.size; // 3, we just removed one value
</pre>

<h3 id="Iterieren_über_ein_Set">Iterieren über ein <code>Set</code></h3>

<pre class="brush: js notranslate">// iterate over items in set
// logs the items in the order: 1, "some text"
for (let item of mySet) console.log(item);

// logs the items in the order: 1, "some text"
for (let item of mySet.keys()) console.log(item);

// logs the items in the order: 1, "some text"
for (let item of mySet.values()) console.log(item);

// logs the items in the order: 1, "some text"
//(key and value are the same here)
for (let [key, value] of mySet.entries()) console.log(key);

// convert set to plain Array
var myArr = Array.from(mySet); // [1, "some text"]

// the following will also work if run in an HTML document
mySet.add(document.body);
mySet.has(document.querySelector("body")); // true

// converting between Set and Array
mySet2 = new Set([1,2,3,4]);
mySet2.size; // 4
[...mySet2]; // [1,2,3,4]

// intersect can be simulated via
var intersection = new Set([...set1].filter(x =&gt; set2.has(x)));

// difference can be simulated via
var difference = new Set([...set1].filter(x =&gt; !set2.has(x)));

// Iterate set entries with forEach
mySet.forEach(function(value) {
  console.log(value);
});

// 1
// 2
// 3
// 4</pre>

<h3 id="Gebräuchliche_Set_Operationen_implementieren">Gebräuchliche <code>Set</code> Operationen implementieren</h3>

<pre class="brush: js line-numbers language-js notranslate"><code class="language-js"><span class="keyword token">function</span> <span class="function token">isSuperset</span><span class="punctuation token">(</span><span class="parameter token"><span class="keyword token">set</span><span class="punctuation token">,</span> subset</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
    <span class="keyword token">for</span> <span class="punctuation token">(</span><span class="keyword token">var</span> elem <span class="keyword token">of</span> subset<span class="punctuation token">)</span> <span class="punctuation token">{</span>
        <span class="keyword token">if</span> <span class="punctuation token">(</span><span class="operator token">!</span><span class="keyword token">set</span><span class="punctuation token">.</span><span class="function token">has</span><span class="punctuation token">(</span>elem<span class="punctuation token">)</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
            <span class="keyword token">return</span> <span class="boolean token">false</span><span class="punctuation token">;</span>
        <span class="punctuation token">}</span>
    <span class="punctuation token">}</span>
    <span class="keyword token">return</span> <span class="boolean token">true</span><span class="punctuation token">;</span>
<span class="punctuation token">}</span>

<span class="keyword token">function</span> <span class="function token">union</span><span class="punctuation token">(</span><span class="parameter token">setA<span class="punctuation token">,</span> setB</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
    <span class="keyword token">var</span> _union <span class="operator token">=</span> <span class="keyword token">new</span> <span class="class-name token">Set</span><span class="punctuation token">(</span>setA<span class="punctuation token">)</span><span class="punctuation token">;</span>
    <span class="keyword token">for</span> <span class="punctuation token">(</span><span class="keyword token">var</span> elem <span class="keyword token">of</span> setB<span class="punctuation token">)</span> <span class="punctuation token">{</span>
        _union<span class="punctuation token">.</span><span class="function token">add</span><span class="punctuation token">(</span>elem<span class="punctuation token">)</span><span class="punctuation token">;</span>
    <span class="punctuation token">}</span>
    <span class="keyword token">return</span> _union<span class="punctuation token">;</span>
<span class="punctuation token">}</span>

<span class="keyword token">function</span> <span class="function token">intersection</span><span class="punctuation token">(</span><span class="parameter token">setA<span class="punctuation token">,</span> setB</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
    <span class="keyword token">var</span> _intersection <span class="operator token">=</span> <span class="keyword token">new</span> <span class="class-name token">Set</span><span class="punctuation token">(</span><span class="punctuation token">)</span><span class="punctuation token">;</span>
    <span class="keyword token">for</span> <span class="punctuation token">(</span><span class="keyword token">var</span> elem <span class="keyword token">of</span> setB<span class="punctuation token">)</span> <span class="punctuation token">{</span>
        <span class="keyword token">if</span> <span class="punctuation token">(</span>setA<span class="punctuation token">.</span><span class="function token">has</span><span class="punctuation token">(</span>elem<span class="punctuation token">)</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
            _intersection<span class="punctuation token">.</span><span class="function token">add</span><span class="punctuation token">(</span>elem<span class="punctuation token">)</span><span class="punctuation token">;</span>
        <span class="punctuation token">}</span>
    <span class="punctuation token">}</span>
    <span class="keyword token">return</span> _intersection<span class="punctuation token">;</span>
<span class="punctuation token">}</span>

<span class="keyword token">function</span> <span class="function token">symmetricDifference</span><span class="punctuation token">(</span><span class="parameter token">setA<span class="punctuation token">,</span> setB</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
    <span class="keyword token">var</span> _difference <span class="operator token">=</span> <span class="keyword token">new</span> <span class="class-name token">Set</span><span class="punctuation token">(</span>setA<span class="punctuation token">)</span><span class="punctuation token">;</span>
    <span class="keyword token">for</span> <span class="punctuation token">(</span><span class="keyword token">var</span> elem <span class="keyword token">of</span> setB<span class="punctuation token">)</span> <span class="punctuation token">{</span>
        <span class="keyword token">if</span> <span class="punctuation token">(</span>_difference<span class="punctuation token">.</span><span class="function token">has</span><span class="punctuation token">(</span>elem<span class="punctuation token">)</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
            _difference<span class="punctuation token">.</span><span class="function token">delete</span><span class="punctuation token">(</span>elem<span class="punctuation token">)</span><span class="punctuation token">;</span>
        <span class="punctuation token">}</span> <span class="keyword token">else</span> <span class="punctuation token">{</span>
            _difference<span class="punctuation token">.</span><span class="function token">add</span><span class="punctuation token">(</span>elem<span class="punctuation token">)</span><span class="punctuation token">;</span>
        <span class="punctuation token">}</span>
    <span class="punctuation token">}</span>
    <span class="keyword token">return</span> _difference<span class="punctuation token">;</span>
<span class="punctuation token">}</span>

<span class="keyword token">function</span> <span class="function token">difference</span><span class="punctuation token">(</span><span class="parameter token">setA<span class="punctuation token">,</span> setB</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
    <span class="keyword token">var</span> _difference <span class="operator token">=</span> <span class="keyword token">new</span> <span class="class-name token">Set</span><span class="punctuation token">(</span>setA<span class="punctuation token">)</span><span class="punctuation token">;</span>
    <span class="keyword token">for</span> <span class="punctuation token">(</span><span class="keyword token">var</span> elem <span class="keyword token">of</span> setB<span class="punctuation token">)</span> <span class="punctuation token">{</span>
        _difference<span class="punctuation token">.</span><span class="function token">delete</span><span class="punctuation token">(</span>elem<span class="punctuation token">)</span><span class="punctuation token">;</span>
    <span class="punctuation token">}</span>
    <span class="keyword token">return</span> _difference<span class="punctuation token">;</span>
<span class="punctuation token">}</span>

<span class="comment token">//Examples</span>
<span class="keyword token">var</span> setA <span class="operator token">=</span> <span class="keyword token">new</span> <span class="class-name token">Set</span><span class="punctuation token">(</span><span class="punctuation token">[</span><span class="number token">1</span><span class="punctuation token">,</span> <span class="number token">2</span><span class="punctuation token">,</span> <span class="number token">3</span><span class="punctuation token">,</span> <span class="number token">4</span><span class="punctuation token">]</span><span class="punctuation token">)</span><span class="punctuation token">,</span>
    setB <span class="operator token">=</span> <span class="keyword token">new</span> <span class="class-name token">Set</span><span class="punctuation token">(</span><span class="punctuation token">[</span><span class="number token">2</span><span class="punctuation token">,</span> <span class="number token">3</span><span class="punctuation token">]</span><span class="punctuation token">)</span><span class="punctuation token">,</span>
    setC <span class="operator token">=</span> <span class="keyword token">new</span> <span class="class-name token">Set</span><span class="punctuation token">(</span><span class="punctuation token">[</span><span class="number token">3</span><span class="punctuation token">,</span> <span class="number token">4</span><span class="punctuation token">,</span> <span class="number token">5</span><span class="punctuation token">,</span> <span class="number token">6</span><span class="punctuation token">]</span><span class="punctuation token">)</span><span class="punctuation token">;</span>

<span class="function token">isSuperset</span><span class="punctuation token">(</span>setA<span class="punctuation token">,</span> setB<span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">// =&gt; true</span>
<span class="function token">union</span><span class="punctuation token">(</span>setA<span class="punctuation token">,</span> setC<span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">// =&gt; Set [1, 2, 3, 4, 5, 6]</span>
<span class="function token">intersection</span><span class="punctuation token">(</span>setA<span class="punctuation token">,</span> setC<span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">// =&gt; Set [3, 4]</span>
<span class="function token">symmetricDifference</span><span class="punctuation token">(</span>setA<span class="punctuation token">,</span> setC<span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">// =&gt; Set [1, 2, 5, 6]</span>
<span class="function token">difference</span><span class="punctuation token">(</span>setA<span class="punctuation token">,</span> setC<span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">// =&gt; Set [1, 2]</span></code></pre>

<h3 id="Array_und_Set"><code>Array</code> und <code>Set</code></h3>

<pre class="brush: js notranslate">var myArray = ["value1", "value2", "value3"];

// Use the regular Set constructor to transform an Array into a Set
var mySet = new Set(myArray);

mySet.has("value1"); // returns true

// Use the spread operator to transform a set into an Array.
console.log([...mySet]); // Will show you exactly the same Array as myArray</pre>

<h3 id="Duplikate_entfernen_aus_einem_Array">Duplikate entfernen aus einem <code>Array</code></h3>

<pre class="brush: js line-numbers language-js notranslate"><code class="language-js"><span class="comment token">// Use to remove duplicate elements from the array </span>

<span class="keyword token">const</span> numbers <span class="operator token">=</span> <span class="punctuation token">[</span><span class="number token">2</span><span class="punctuation token">,</span><span class="number token">3</span><span class="punctuation token">,</span><span class="number token">4</span><span class="punctuation token">,</span><span class="number token">4</span><span class="punctuation token">,</span><span class="number token">2</span><span class="punctuation token">,</span><span class="number token">3</span><span class="punctuation token">,</span><span class="number token">3</span><span class="punctuation token">,</span><span class="number token">4</span><span class="punctuation token">,</span><span class="number token">4</span><span class="punctuation token">,</span><span class="number token">5</span><span class="punctuation token">,</span><span class="number token">5</span><span class="punctuation token">,</span><span class="number token">6</span><span class="punctuation token">,</span><span class="number token">6</span><span class="punctuation token">,</span><span class="number token">7</span><span class="punctuation token">,</span><span class="number token">5</span><span class="punctuation token">,</span><span class="number token">32</span><span class="punctuation token">,</span><span class="number token">3</span><span class="punctuation token">,</span><span class="number token">4</span><span class="punctuation token">,</span><span class="number token">5</span><span class="punctuation token">]</span>

console<span class="punctuation token">.</span><span class="function token">log</span><span class="punctuation token">(</span><span class="punctuation token">[</span><span class="operator token">...</span>new <span class="class-name token">Set</span><span class="punctuation token">(</span>numbers<span class="punctuation token">)</span><span class="punctuation token">]</span><span class="punctuation token">)</span>

<span class="comment token">// [2, 3, 4, 5, 6, 7, 32]</span></code></pre>

<h3 id="String_und_Set"><code>String</code> und <code>Set</code></h3>

<pre class="brush: js line-numbers language-js notranslate"><code class="language-js"><span class="keyword token">var</span> text <span class="operator token">=</span> <span class="string token">'India'</span><span class="punctuation token">;</span>

<span class="keyword token">var</span> mySet <span class="operator token">=</span> <span class="keyword token">new</span> <span class="class-name token">Set</span><span class="punctuation token">(</span>text<span class="punctuation token">)</span><span class="punctuation token">;</span>  <span class="comment token">// Set ['I', 'n', 'd', 'i', 'a']</span>
mySet<span class="punctuation token">.</span>size<span class="punctuation token">;</span>  <span class="comment token">// 5</span></code></pre>

<h2 id="Spezifikationen">Spezifikationen</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Spezifikation</th>
   <th scope="col">Status</th>
   <th scope="col">Kommentar</th>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-set-objects', 'Set')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-set-objects', 'Set')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td></td>
  </tr>
 </tbody>
</table>

<h2 id="Browserkompatibilität"><a id="browserkompatibilität" name="browserkompatibilität"></a>Browserkompatibilität</h2>



<p>{{Compat("javascript.builtins.Set")}}</p>

<h2 id="Siehe_auch">Siehe auch</h2>

<ul>
 <li>{{jsxref("Map")}}</li>
 <li>{{jsxref("WeakMap")}}</li>
 <li>{{jsxref("WeakSet")}}</li>
</ul>