在jQuery和javascript中选择父级的前0-n个子级的最佳性能

Question

I want to select the first n children under a specific parent. For this case I don't want to use each index unless its the best performance.

Example:

// select first 20 child elements
var twentyChildElements = $("div").children("span(20)"); 

<div>
 <span index="1"/>
 <span index="2"/>
 <span index="3"/>
....
 <span index="n"/>
</div>

Answer 1

You can use the :lt pseudo-selector:

var twentyChildElements = $("div > span:lt(20)");

> means immediate children , and :lt(2) means the first 20 elements that match the selector (it's zero-based, so this returns elements 0 through 19).

Answer 2

Just use jQuery's slice :

var twentyChildElements = $("div").children("span").slice(0, 20); 

See also this performance test case - it's always faster than :lt(n) , but can be outperformed by native selector engines.

Answer 3

您可以使用:lt方法：

$("div").children("span:lt(n)")

Answer 4

Go fancy... Let css do the job! ;)

Use a negative nth-child combinator selector. MDN nth-child selector

var twentyChildElements = $("div > span:nth-child(-n+20)");