jQuery：检测元素是否存在
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jQuery: Detect if element exists
提问by st4ck0v3rfl0w
In my code I have the following html that gets appended to a List Item when the user clicks on a specific element.
在我的代码中，当用户单击特定元素时，我将以下 html 附加到列表项。
<span class="greenCheckMark"></span>
Using jQuery, how would I detect if the element existed, and if so, not add another green checkmark?
使用 jQuery，我如何检测元素是否存在，如果存在，不添加另一个绿色复选标记？
$('.clickedElement').live('click',function(){
//does the green check mark exist? if so then do nothing, else
$('#listItem).append('<span class="greenCheckMark"></span>');
});
回答by Adam
回答by TJ Koblentz
You could just look for it?
你就随便找找？
($('.greenCheckMark', '#listItem').length > 0) ? /* found green check mark in #listItem */ : /* not found */ ;
EDIT: Fixed 'un-relatedness' to question.
编辑：修复了问题的“不相关性”。
回答by James
As per your requirements, this will only append the <span>in the case that #listItemdoes not already contain a <span>with a classof greenCheckMark.
按您的要求，这样只会追加<span>在该情况下，#listItem尚不包含<span>了class的greenCheckMark。
var listItem = $('#listItem');
if ( !listItem.find('span.greenCheckMark')[0] ) {
listItem.append('<span class="greenCheckMark"></span>');
}
回答by Alex Larzelere
$('.clickedElement').live('click',function(){
//does the green check mark exist? if so then do nothing, else
if($("#listItem span.greenCheckMark").length != 0)
{
$('#listItem').append('<span class="greenCheckMark"></span>');
}
});
Okay, after a few edits, this should be what you're looking for.
好的，经过几次编辑后，这应该就是您要查找的内容。
$("#listItem span.greenCheckMark").length != 0will return an array of JQuery objects, if that area has a length not equal to 0 then it exists. Make sure that you are checking specifically for where you want to check, ($("span.greenCheckMark").lengthwill check the entire document for green check marks).
$("#listItem span.greenCheckMark").length != 0将返回一个 JQuery 对象数组，如果该区域的长度不等于 0，则它存在。确保您专门检查要检查的位置，（$("span.greenCheckMark").length将检查整个文档是否有绿色复选标记）。
