问题
Quick question, is a jQuery child selector without a parent ever valid? If so, how would you use it?
Example of the jQuery child selector:
$('ul > li')
Example of jQuery child selector without parent:
$('> li')
The second example above doesn't work. However I can't remember if I saw it in the past before or I've seen something advance like:
$('ul').not('>li')
Doesn't really work either (but doesn't pop up an error message, so it's just ignored?)
So my question is would you EVER use a child selector without a parent, and have it be a valid jQuery selector.
Thanks, sorry if question is dumb. :)
Edit:
Along with Nick's jQuery.find example on the bottom, another use case is
$('ul:has(>li)')
Note: that $('ul').has('>li') is wrong and should be written
$('ul').has('ul>li')
AND for not()
Not sure if I have it correct, but you wouldn't ever use a > inside of not() directy because not() only concern about one element, while > compares multiple elements. However you can do something like
$('li:not(:has(>p))'
回答1:
Yes it works without a parent, but it can't be on the default context, because your <li> isn't a direct child of a document. Also, it wouldn't make any sense by itself really, since it's a direct child of something, it'd be the same as $("li").
When would it be used? possibly to cut down on code, for example:
$(this).find("> li > span a");
//as opposed to not being able to start with it:
$(this).children("li").children("span").find("a");
回答2:
I cannot think of a situation that requires a child selector without a parent. The child selector is used to select immediate children of a parent element. If there is no parent element, whose children should be selected?
回答3:
Why would you ever want that ?
You could always use $('* > li') although i can't really see what that would accomplish, as li should always be a child of something ul or ol
来源：https://stackoverflow.com/questions/3992473/jquery-child-selector-without-a-parent-allowed