如果不存在,jQuery追加 [英] jQuery append if doesn't exist
本文介绍了如果不存在,jQuery追加的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我想附加一个 div
只有它还没有。我正在尝试这个但它不起作用:
I would like to append a div
only if it's not already there. I am trying with this but it doesn't work:
$('#method_id').on('change', function (e) {
if ($(this).find("option:selected").data('method-column-id') != 1) {
if ($('#column_message').next('div').length)
$('#column_message')
.append('<div id="warning_message" class="alert alert-danger"><strong>Warning!</strong> Installed column and method do not match</div>');
} else {
$('.form-group').find('#column_message>.alert').remove();
}
});
如果我删除第二个if子句,每当我选择一个通过的选项时它会被追加第一个if子句
And if I remove the second if-clause, it gets appended every time I select an option which passes first if-clause
这是HTML
<!-- Warning message -->
<div class="form-group">
<label for="group" class="col-md-2 control-label"></label>
<div id="column_message" class="col-md-6">
</div>
</div>
推荐答案
为了检查元素是否存在,你需要找到一个只匹配该元素的选择器,并检查jQuery对象的长度是否等于0,如下所示:
In order to check if an element exists, you need to find a selector that matches only that element and check if the length of the jQuery object is equal to 0 or not, like so:
if ($('#unique-selector').length === 0) {
// code to run if it isn't there
}
else {
// code to run if it is there
}
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