blocks|key|338454|text|如果没有这样的元素，则getElementById返回null。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|338455|entityMap^0|B|E|R|4|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

<code>getElementById</code> returns <code>null</code> if there is no such element.

blocks|key|554478|text|尝试获取ID为的元素，并检查返回值是否为空：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|554479|document.getElementById('some_nonexistent_id')+===+null|code-block|syntax|javascript|554480|如果您使用的是jQuery，则可以执行以下操作：|554481|$('#some_nonexistent_id').length+===+0|554482|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Try getting the element with the ID and check if the return value is null:

<pre><code>document.getElementById('some_nonexistent_id') === null
</code></pre>

If you're using jQuery, you can do:

<pre><code>$('#some_nonexistent_id').length === 0
</code></pre>

blocks|key|338541|text|if+(!document.getElementById("given-id"))+{
//It+does+not+exist
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|338542|如果带有given-id的元素不存在，则语句document.getElementById("given-id")返回null，而null是falsy，这意味着在if语句中求值时，它将转换为false。(other+falsy+values)|unstyled|offset|length|style|CODE|338543|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Glossary/Falsy^0|0|4|8|M|Z|1N|4|1T|4|2U|I|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|T|8|@$G|U|H|V|I|J]|$G|W|H|X|I|J]|$G|Y|H|Z|I|J]|$G|10|H|11|I|J]]|9|@$G|12|H|13|1|14]]|A|$]]|$1|K|3|-4|5|F|7|15|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

<pre><code>if (!document.getElementById("given-id")) {
//It does not exist
}
</code></pre>

The statement <code>document.getElementById("given-id")</code> returns <code>null</code> if an element with <code>given-id</code> doesn't exist, and <code>null</code> is falsy meaning that it translates to false when evaluated in an if-statement. (<a href="https://developer.mozilla.org/en-US/docs/Glossary/Falsy" rel="noreferrer">other falsy values</a>)

blocks|key|338566|text|var+myElem+=+document.getElementById('myElementId');
if+(myElem+===+null)+alert('does+not+exist!');|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|338567|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>var myElem = document.getElementById('myElementId');
if (myElem === null) alert('does not exist!');
</code></pre>

blocks|key|554582|text|它适用于：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|554583|+var+element+=+document.getElementById('myElem');
+if+(typeof+(element)+!=+undefined+&&+typeof+(element)+!=+null+&&+typeof+(element)+!=+'undefined')+{
+++++console.log('element+exists');
+}
+else{
+++++console.log('element+NOT+exists');
+}|code-block|syntax|javascript|554584|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

That works with :

<pre><code> var element = document.getElementById('myElem');
 if (typeof (element) != undefined &amp;&amp; typeof (element) != null &amp;&amp; typeof (element) != 'undefined') {
 console.log('element exists');
 }
 else{
 console.log('element NOT exists');
 }
</code></pre>

blocks|key|338617|text|检查我的JavaScript和JQuery代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|338618|JavaScript：|338619|if+(!document.getElementById('MyElementId')){
++++alert('Does+not+exist!');
}|code-block|syntax|javascript|338620|JQuery：|338621|if+(!$("#MyElementId").length){
++++alert('Does+not+exist!');
}|338622|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Check both my JavaScript and JQuery code :

JavaScript:

<pre><code>if (!document.getElementById('MyElementId')){
 alert('Does not exist!');
}
</code></pre>

JQuery:

<pre><code>if (!$("#MyElementId").length){
 alert('Does not exist!');
}
</code></pre>

blocks|key|554676|text|还有一个更好的解决方案。您甚至不需要检查元素是否返回null。您可以简单地执行以下操作：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|554677|if+(document.getElementById('elementId'))+{
++console.log('exists')
}|code-block|syntax|javascript|554678|只有当元素实际存在于DOM中时，该代码才会将exists记录到控制台。|554679|entityMap^0|Q|4|0|0|M|6|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

There's an even better solution. You don't even need to check if the element returns <code>null</code>. You can simply do this:

<pre><code>if (document.getElementById('elementId')) {
 console.log('exists')
}
</code></pre>

That code will only log <code>exists</code> to console if the element actually exists in the DOM.

blocks|key|338712|text|我在下面这样做，并检查id是否存在，如果存在，则执行函数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|338713|var+divIDVar+=+$('#divID').length;
if+(divIDVar+===+0){+
++++console.log('No+DIV+Exist');+
}+else{++
++++FNCsomefunction();+
}+++|code-block|syntax|javascript|338714|entityMap^0|B|2|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

I do below and check if <code>id</code> exist and execute function if exist.

<pre><code>var divIDVar = $('#divID').length;
if (divIDVar === 0){ 
 console.log('No DIV Exist'); 
} else{ 
 FNCsomefunction(); 
} 
</code></pre>

Checking if a div exists is fairly simple

<pre><code>if(document.getif(document.getElementById('if')){

}
</code></pre>

But how can I check if a div with the given id does not exist?

Check if a div does NOT exist with javascript

jQuery

检查是否存在div相当简单if(document.getif(document.getElementById('if')){}但是如何检查具有给定id的div是否不存在呢？

问使用javascript检查div是否不存在
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问使用javascript检查div是否不存在EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问使用javascript检查div是否不存在
EN