问题
I don't unterstand this syntax:
var dir = $("a.store").parents("table")[0];
var stores = $("a.store:has(b)", dir);
What will store contain?
What is the meaning of "$("a.store:has(b)", dir);"?
回答1:
It will return a collection of dom elements that match the css selector ("a.store:has(b)") that are children of the dom element stored in the 'dir' variable.
回答2:
In your example, dir is the context of the selector. From the docs linked by Felix in his comment:
By default, selectors perform their searches within the DOM starting at the document root. However, an alternate context can be given for the search by using the optional second parameter to the $() function. For example, to do a search within an event handler, the search can be restricted like so:
$('div.foo').click(function() { $('span', this).addClass('bar'); });
回答3:
From the jquery docs,
:has() Selector
Selects elements which contain at least one element that matches the specified selector.
The expression $('div:has(p)') matches a
<div>if a<p>exists anywhere among its descendants, not just as a direct child.
http://api.jquery.com/has-selector/
Regarding the second parameter to jQuery, it is the context. It can be a DOM element on which the selector operates.
In your case:
var dir will have a table which is parent of <a class="store" ...
the store variable will contain only those <a class="store" .. which have a <b> inside them.
回答4:
$("a.store")
Will get all <a> elements that have the class .store
.parents("table")[0];
Will get the table(s) these <a> reside in.
$("a.store:has(b)", dir);
Will find all <a> elements that have the class .store and contain a <b> element, using the previously found tables dir as context, meaning that instead of going through the entire document to find matches, it will only go through these tables.
回答5:
In its simplest form..
Its equivalent to doing..
$('someParent').find('.matchingDescendants');
来源：https://stackoverflow.com/questions/6479300/what-does-class-for-the-same-element-element-mean