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diff --git a/files/nl/web/javascript/reference/global_objects/null/index.html b/files/nl/web/javascript/reference/global_objects/null/index.html new file mode 100644 index 0000000000..4a5abdaa2d --- /dev/null +++ b/files/nl/web/javascript/reference/global_objects/null/index.html @@ -0,0 +1,124 @@ +--- +title: 'null' +slug: Web/JavaScript/Reference/Global_Objects/null +translation_of: Web/JavaScript/Reference/Global_Objects/null +--- +<div>{{jsSidebar("Objects")}}</div> + +<p>De waarde <code>null</code> representeert het moedwillig weglaten, of de bedoelde afwezigheid van welk object of waarde dan ook. Het is een van JavaScript's {{Glossary("Primitive", "primitive values")}}.</p> + +<h2 id="Syntax">Syntax</h2> + +<pre class="syntaxbox"><code>null </code></pre> + +<h2 id="Beschrijving">Beschrijving</h2> + +<p>De waarde <code>null</code> wordt letterlijk geschreven als <code>null</code> (het is geen idenfifier voor een eigenschap van de global object zoals {{jsxref("Global_Objects/undefined","undefined")}} wel kan zijn). In APIs, wordt <code>null</code> vaak verkregen op plekken waar een object mag worden verwacht, maar waar tegelijk geen object relevant is . Wanneer op null of undefined wordt gecontroleerd, wees dan bewust van de <a href="/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators">verschillen tussen equality (==) en identity (===) operators</a> (type-conversie wordt via de eerste bereikt).</p> + +<pre class="brush: js">// foo does not exist. It is not defined and has never been initialized: +> foo +"ReferenceError: foo is not defined" + +// foo is known to exist now but it has no type or value: +> var foo = null; foo +"null" +</pre> + +<h3 id="Verschil_tussen_null_en_undefined">Verschil tussen <code>null</code> en <code> undefined</code></h3> + +<pre class="brush: js">typeof null // object (bug in ECMAScript, should be null) +typeof undefined // undefined +null === undefined // false +null == undefined // true +</pre> + +<h2 id="Specificaties">Specificaties</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">Specificatie</th> + <th scope="col">Status</th> + <th scope="col">Commentaar</th> + </tr> + <tr> + <td>{{SpecName('ES1')}}</td> + <td>{{Spec2('ES1')}}</td> + <td>Initial definition.</td> + </tr> + <tr> + <td>{{SpecName('ES5.1', '#sec-4.3.11', 'null value')}}</td> + <td>{{Spec2('ES5.1')}}</td> + <td> </td> + </tr> + <tr> + <td>{{SpecName('ES6', '#sec-null-value', 'null value')}}</td> + <td>{{Spec2('ES6')}}</td> + <td> </td> + </tr> + <tr> + <td>{{SpecName('ESDraft', '#sec-null-value', 'null value')}}</td> + <td>{{Spec2('ESDraft')}}</td> + <td> </td> + </tr> + </tbody> +</table> + +<h2 id="Browser_compatibiliteit">Browser compatibiliteit</h2> + +<p>{{CompatibilityTable}}</p> + +<div id="compat-desktop"> +<table class="compat-table"> + <tbody> + <tr> + <th>Feature</th> + <th>Chrome</th> + <th>Firefox (Gecko)</th> + <th>Internet Explorer</th> + <th>Opera</th> + <th>Safari</th> + </tr> + <tr> + <td>Basic support</td> + <td>{{CompatVersionUnknown}}</td> + <td>{{CompatVersionUnknown}}</td> + <td>{{CompatVersionUnknown}}</td> + <td>{{CompatVersionUnknown}}</td> + <td>{{CompatVersionUnknown}}</td> + </tr> + </tbody> +</table> +</div> + +<div id="compat-mobile"> +<table class="compat-table"> + <tbody> + <tr> + <th>Feature</th> + <th>Android</th> + <th>Chrome for Android</th> + <th>Firefox Mobile (Gecko)</th> + <th>IE Mobile</th> + <th>Opera Mobile</th> + <th>Safari Mobile</th> + </tr> + <tr> + <td>Basic support</td> + <td>{{CompatVersionUnknown}}</td> + <td>{{CompatVersionUnknown}}</td> + <td>{{CompatVersionUnknown}}</td> + <td>{{CompatVersionUnknown}}</td> + <td>{{CompatVersionUnknown}}</td> + <td>{{CompatVersionUnknown}}</td> + </tr> + </tbody> +</table> +</div> + +<h2 id="Zie_ook">Zie ook</h2> + +<ul> + <li>{{jsxref("undefined")}}</li> + <li>{{jsxref("NaN")}}</li> +</ul> |
