blocks|key|1458603|text|试试这个..。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1458604|$('select+option:first-child').attr("selected",+"selected");|code-block|syntax|javascript|1458605|另一种选择是这样，但它一次只适用于一个下拉列表，如下所示：|1458606|var+myDDL+=+$('myID');
myDDL[0].selectedIndex+=+0;|1458607|看看这篇关于如何基于值进行设置的文章，它很有趣，但对这个特定的问题没有帮助：|1458608|Change+the+selected+value+of+a+drop-down+list+with+jQuery|offset|length|1458609|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/499405/change-selected-value-of-drop-down-list-with-jquery^0|0|0|0|0|0|0|1L|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|12|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|13|8|@]|9|@$O|14|P|15|1|16]]|A|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

Try this out...

<pre><code>$('select option:first-child').attr("selected", "selected");
</code></pre>

Another option would be this, but it will only work for one drop down list at a time as coded below:

<pre><code>var myDDL = $('myID');
myDDL[0].selectedIndex = 0;
</code></pre>

Take a look at this post on how to set based on value, its interesting but won't help you for this specific issue:

<a href="https://stackoverflow.com/questions/499405/change-selected-value-of-drop-down-list-with-jquery">Change the selected value of a drop-down list with jQuery</a>

blocks|key|1458581|text|您的选择器错误，您可能正在查找|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1458582|$('select+option:nth-child(1)')|code-block|syntax|javascript|1458583|这也是可行的：|1458584|$('select+option:first-child')|1458585|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|$]]

Your selector is wrong, you were probably looking for

<pre><code>$('select option:nth-child(1)')
</code></pre>

This will work also:

<pre><code>$('select option:first-child')
</code></pre>

blocks|key|1243996|text|如果存在'onchange'事件，则会触发RSolgberg的另一种解决方案：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1243997|$("#target").val($("#target+option:first").val());|code-block|syntax|javascript|1243998|How+to+make+first+option+of++selected+with+jQuery?|1243999|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/1414276/how-to-make-first-option-of-select-selected-with-jquery^0|4|A|0|0|0|1E|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

Ana alternative Solution for RSolgberg, which fires the <code>'onchange'</code> event if present:

<pre><code>$("#target").val($("#target option:first").val());
</code></pre>

<a href="https://stackoverflow.com/questions/1414276/how-to-make-first-option-of-select-selected-with-jquery">How to make first option of &lt;select &gt; selected with jQuery?</a>

blocks|key|1243966|text|$("#DDLID").val(+$("#DDLID+option:first-child").val()+);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1243967|For+Complete+Drop+Down+List+Operations+using+Jquery|unstyled|offset|length|1243968|entityMap|0|LINK|mutability|MUTABLE|url|http://knowfreely.com/index.php?option=com_content&view=article&id=228%253adrop-down-list-operations-in-jquery&catid=20%253ajquery-and-net&Itemid=39^0|0|0|1F|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|R|8|@]|9|@$G|S|H|T|1|U]]|A|$]]|$1|I|3|-4|5|F|7|V|8|@]|9|@]|A|$]]]|J|$K|$5|L|M|N|A|$O|P]]]]

<pre><code>$("#DDLID").val( $("#DDLID option:first-child").val() );
</code></pre>

<a href="http://knowfreely.com/index.php?option=com_content&amp;view=article&amp;id=228%3adrop-down-list-operations-in-jquery&amp;catid=20%3ajquery-and-net&amp;Itemid=39" rel="nofollow">For Complete Drop Down List Operations using Jquery</a>

blocks|key|1458633|text|你想要的可能是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1458634|$("select+option:first-child")|code-block|syntax|javascript|1458635|这段代码是什么|1458636|attr("selected",+"selected");|1458637|所做的就是将“选定”属性设置为“选定”。|1458638|如果您想要选定的选项，无论它是否是第一个子项，选择器都是：|1458639|$("select").children("[selected]")|1458640|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

What you want is probably:

<pre><code>$("select option:first-child")
</code></pre>

What this code

<pre><code>attr("selected", "selected");
</code></pre>

is doing is setting the "selected" attribute to "selected"

If you want the selected options, regardless of whether it is the first-child, the selector is:

<pre><code>$("select").children("[selected]")
</code></pre>

blocks|key|1244109|text|下面是一个简单的javascript解决方案，它在大多数情况下都有效：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1244110|document.getElementById("selectId").selectedIndex+=+"0";|code-block|syntax|javascript|1244111|entityMap^0|8|A|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|$]]

Here is a simple <code>javascript</code> solution which works in most cases:

<pre><code>document.getElementById("selectId").selectedIndex = "0";
</code></pre>

blocks|key|1244083|text|我之所以回答，是因为之前的答案已经不再适用于最新版本的jQuery。我不知道它什么时候停止工作的，但是文档说从jQuery+1.6开始，.prop()就一直是获取/设置属性的首选方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1244084|这就是我如何让它工作的(使用jQuery+3.2.1)：|1244085|$('select+option:nth-child(1)').prop("selected",+true);|code-block|syntax|javascript|1244086|我使用的是knockoutjs，上面的代码没有触发更改绑定，所以我在末尾添加了.change()。|1244087|以下是我的解决方案所需要的：|1244088|$('select+option:nth-child(1)').prop("selected",+true).change();|1244089|请参阅文档中的.prop()注释：http://api.jquery.com/prop/|offset|length|1244090|entityMap|0|LINK|mutability|MUTABLE|url|http://api.jquery.com/prop/^0|0|0|0|0|0|0|H|R|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|15|8|@]|9|@]|A|$G|H]]|$1|O|3|P|5|6|7|16|8|@]|9|@$Q|17|R|18|1|19]]|A|$]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

I'm answering because the previous answers have stopped working with the latest version of jQuery. I don't know when it stopped working, but the documentation says that .prop() has been the preferred method to get/set properties since jQuery 1.6.

This is how I got it to work (with jQuery 3.2.1):

<pre><code>$('select option:nth-child(1)').prop("selected", true);
</code></pre>

I am using knockoutjs and the change bindings weren't firing with the above code, so I added .change() to the end.

Here's what I needed for my solution:

<pre><code>$('select option:nth-child(1)').prop("selected", true).change();
</code></pre>

See .prop() notes in the documentation here: <a href="http://api.jquery.com/prop/" rel="nofollow noreferrer">http://api.jquery.com/prop/</a>

blocks|key|1243948|text|如果您想要检查所选选项的文本，而不管它是否是第一个子项。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1243949|var+a+=+$("#select_id+option:selected").text();
alert(a);+//check+if+the+value+is+correct.
if(a+==+"value")+{--+execute+code+--}|code-block|syntax|javascript|1243950|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|$]]

if you want to check the text of selected option regardless if its the 1st child.

<pre><code>var a = $("#select_id option:selected").text();
alert(a); //check if the value is correct.
if(a == "value") {-- execute code --}
</code></pre>

blocks|key|1458783|text|++++var+arr_select_val=[];

++++$("select").each(function()+{+
++++++++var+name=this.name;
++++++++++++arr_select_val[name]=$('select+option:first-child').val();
++++});


//+Process+the+array+object
+++++$('.orders_status_summary_div').print(arr_select_val);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1458784|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 arr_select_val=[];

 $("select").each(function() { 
 var name=this.name;
 arr_select_val[name]=$('select option:first-child').val();
 });


// Process the array object
 $('.orders_status_summary_div').print(arr_select_val);
</code></pre>

I want to know how to select the first option in all select tags on my page using jquery.

tried this:

<pre><code>$('select option:nth(0)').attr("selected", "selected"); 
</code></pre>

But didn't work

How to select the first element in the dropdown using jquery?

我想知道如何使用jquery在我的页面上选择所有select标记中的第一个选项。我试过了：$('select option:nth(0)').attr("selected", "selected"); 但没有起作用

问如何使用jquery选择下拉列表中的第一个元素？
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问如何使用jquery选择下拉列表中的第一个元素？EN

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问如何使用jquery选择下拉列表中的第一个元素？
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