问题描述
据我了解，在查询中添加.first()或:first不会在第一个匹配项后停止DOM搜索.它只是告诉jQuery从匹配的集合中取出第一个元素.
From what I understand, adding .first() or :first to a query doesn't stop DOM search after the first match. It just tells jQuery to take 1st element out of matched collection.
如果是这样，那么有没有办法在第一个匹配项之后停止DOM搜索?例如，如果我知道此查询的结果将始终是单个元素，那么如何告诉jQuery不要浪费时间进行进一步的搜索?
If that is true, then is there a way to stop DOM search after the first match? For example, if I know that the result of this query will always be a single element, how can jQuery be told to not waste time searching further?
推荐答案
据我所知，目前尚无法在jQuery中进行此操作.最好的方法是$(selector).first()，其中selector是标准CSS选择器，不包括任何Sizzle特定的选择器(因此请不要使用:first).在这种情况下，jQuery在现代浏览器中使用快速DOM querySelectorAll方法.
As far as I know there's no way to do this in jQuery at the moment. The best you can do is $(selector).first(), where selector is a standard CSS selector not including any Sizzle-specific selectors (so don't use :first). In this case jQuery uses the fast DOM querySelectorAll method in modern browsers.
您可以使用DOM querySelector方法手动获得优化，该方法被构建为仅选择第一个匹配项:
You can get the optimisation manually by using the DOM querySelector method which is built to select only the first match:
$.getFirst= function(selector) {
if ('querySelector' in document)
return $(document.querySelector(selector));
else
return $(selector).first();
}
但是，这样做所节省的金额要比确保使用querySelectorAll所节省的金额小得多.
however the amount you'll save by doing this is much smaller than the amount you save by making sure querySelectorAll can be used.
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