最合适的方法：$（$（" .answer"）[0]） [英] Most appropriate way to get this: $($(".answer")[0])
问题描述
假设我想获得该类所有元素中的第一个元素.answer
Suppose I want to get the first element amongst all the elements of the class ".answer"
$($(".answer")[0])
我可以做到以上，但最佳平衡是什么优雅和速度之间？
I can do the above, but what is the best balance between elegance and speed?
*改变了问题以反映当前的讨论
*changed the question to reflect the current discussion
推荐答案
以下都是功能相同的（虽然不是速度）：
The following are all equivalent in functionality (though not speed):
-
var a0 = $（ $（'。answer'）[0]）; -
var a0 = $（'。answer'）。first（） ;- 请参阅 http://api.jquery.com/first/ -
var a0 = $（'。answer：first'）;- 参见 http://api.jquery.com/first-selector/ -
var a0 = $（'。answer'）。eq（0）;- 参见 HTTP： //api.jquery.com/eq/ -
var a0 = $（'。answer：eq（0）'）;- 请参阅 http://api.jquery.com/eq-selector/
var a0 = $($('.answer')[0]);var a0 = $('.answer').first();- see http://api.jquery.com/first/var a0 = $('.answer:first');- see http://api.jquery.com/first-selector/var a0 = $('.answer').eq(0);- see http://api.jquery.com/eq/var a0 = $('.answer:eq(0)');- see http://api.jquery.com/eq-selector/
哪个最好？
已假设选择器版本应该比方法版本更快（并且逻辑有一定意义）但我还没有找到可靠的跨浏览器，多文档基准测试，证明这是真的。
Which is the best?
It has been hypothesized that the selector versions should be faster than the method versions (and the logic makes some sense) but I have not yet found a reliable cross-browser, multi-document benchmark that proves this to be true.
在某些情况下，你不能使用选择器，因为你有一个由链式结果产生的jQuery对象，后来必须将其削减。
编辑：根据以下@ yc测试的优秀信息，以下是当前（2011年2月4日）的测试结果，总结并与基准<$ c $进行比较c> .answer：first ：
Edit: Based on the excellent information from @yc's tests below, following are the current (2011-Feb-4) test results summarized and compared against a baseline of .answer:first:
:first :eq(0) .first() .eq(0) $($('...')[0])
Chrome 8+ 100% 92% 224% 266% 367%
FF 3.6 100% 100% 277% 270% 309%
FF 4.0b 100% 103% 537% 521% 643%
Safari 5 100% 93% 349% 352% 467%
Opera 11 100% 103% 373% 374% 465%
IE 8 100% 101% 1130% 1246% 1767%
iPhone 4 100% 95% 269% 316% 403%
=====================================================
Weighted 100% 92% 286% 295% 405%
Major 100% 95% 258% 280% 366%
- 加权行显示按每个浏览器的测试次数加权的性能;流行的浏览器（在这些测试中）计算得更强。
- 主要行显示相同，仅包括主要桌面浏览器的非beta版本。
- The Weighted line shows the performance weighted by the number of tests per browser; popular browsers (among those testing) are counted more strongly.
- The Major line shows the same, only including non-beta releases of the major desktop browsers.
总结：假设（目前）是错误的。这些方法明显快于Sizzle选择器，并且几乎没有例外，OP的代码 $（$（'。answer'）[0]）是最快的！
In summary: the hypothesis is (currently) wrong. The methods are significantly faster than the Sizzle selectors, and with almost no exception the OP's code $($('.answer')[0]) is the fastest of them all!
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