jQuery是否对“选择器"进行某种形式的缓存? [英] Does jQuery do any kind of caching of "selectors"?

问题描述

例如，第一段代码会执行两次完整搜索吗?如果没有发生DOM更改，是否足够聪明地缓存结果?

For example, will the first piece of code perform a full search twice, or is it smart enough to cache results if no DOM changes have occurred?

if ($("#navbar .heading").text() > "") {
  $("#navbar .heading").hide();
}

和

var $heading = $("#navbar .heading");

if ($heading.text() > "") {
  $heading.hide();
}

如果选择器更复杂，我可以想象这是一个不小的成功.

If the selector is more complex I can imagine it's a non-trivial hit.

推荐答案

jQuery没有，但是有可能在表达式中分配变量，然后在后续表达式中重用它们.因此，对您的示例进行缓存处理...

jQuery doesn't, but there's the possibility of assigning to variables within your expression and then use re-using those in subsequent expressions. So, cache-ifying your example ...

if ((cached = $("#navbar .heading")).text() > "") {
  cached.hide();
}

不利的一面是它使代码更加笨拙且难以理解.

Downside is it makes the code a bit fuglier and difficult to grok.

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