问题
Are there any speed/efficiency differences between the following two lines.
$("table td:not(:first-child)")
and
$("table td").not(":first-child")
I would think that the first would be better since it is removes objects, but is there an actual difference and is it substantial.
Thanks
回答1:
As you can see from the jsperf test, :not is on average about twice as fast. Overall though this performance will likely be a very small part of your overall execution time.
The jquery docs state:
The .not() method will end up providing you with more readable selections than pushing complex selectors or variables into a :not() selector filter. In most cases, it is a better choice.
So really it's up to you to decide if the fractions of a second you gain outweigh the readability.
回答2:
Depends on the browser.
Browsers that support querySelectorAll will get a performance boost with...
$("table td:not(:first-child)")
...because it is a valid selector. Older browsers (IE7 and lower) will not.
You need to be careful with the :not() selector though. jQuery (Sizzle) extends it with non-standard selectors, so it's easy to break qSA.
来源：https://stackoverflow.com/questions/8845811/performance-differences-between-using-not-and-not-selectors