Select pseudo-elements with jquery [duplicate]

问题

How would you convert this block of css into jquery?

.nav li a:first-child:nth-last-child(2):before { 
    content:""; 
    position: absolute; 
    height:0; 
    width: 0; 
    border: 5px solid transparent; 
    top: 50% ;
    right:5px;  
}

I've tried a couple different ways but nothing I tried worked properly. Where this css selects only before the the jquery selects the whole anchor.

$(".nav li a:first-child:nth-last-child(2)").before().css(...); // did not work

$(".nav li a:first-child:nth-last-child(2)").before(function(){
    $(this).css(...);
}); // did not work

I tried a lot of other stuff as well, let me know what you guys think, Thanks!

HTML:

<ul class="nav">
    <li><a href="index.php">Home</a></li>
    <li><a href="index.php">Class Assignments</a>
        <ul>
            <li><a href="#">Java</a>
                <ul>
                    <li><a href="java1.php">Java 1</a></li>
                    <li><a href="java2.php">Java 2</a></li>
                    <li><a href="java3.php">Java 3</a></li>
                    <li><a href="java4.php">Java 4</a></li>
                </ul>
            </li>
            <li><a href="#">JavaScript</a>
                <ul>
                    <li><a href="javaScript1.php">JavaScript 1</a></li>
                    <li><a href="javaScript2.php">JavaScript 2</a></li>
                    <li><a href="javaScript3.php">JavaScript 3</a></li>
                    <li><a href="javaScript4.php">JavaScript 4</a></li>
                </ul>
            </li>
            <li><a href="#">PHP</a></li>
            <li><a href="#">C#</a></li>
        </ul>
    </li>
    <li><a href="index.php">Projects</a>
        <ul>
            <li><a href="project.php">Project</a></li>
            <li><a href="project.php">Project</a></li>
            <li><a href="project.php">Project</a></li>
            <li><a href="project.php">Project</a></li>
        </ul>
    </li>
    <li><a href="index.php">Contact</a></li>
</ul>

This is what it looks like with the css...

回答1:

Not sure that would work exactly the same as with :before, but what if you used jQuery to insert a <span>-tag instead, and then adjust the CSS of the <span>? I.e.

$(".nav li a:first-child:nth-last-child(2)").prepend('<span class="before-hack" />');
$('.before-hack').css(...);

Here's a fiddle: http://jsfiddle.net/Niffler/287y3s4s/9/

回答2:

Javascript can't modify :before, :after pseudoselectors.

Solution for your problem is add css rules directly to css file. https://developer.mozilla.org/en-US/docs/Web/API/document.styleSheets

回答3:

First store the css into an object:

     var css =
            {
           "content":"",
           "position":"absolute",
           "height":"0",
           "width":"0", 
           "border":"5px solid transparent",
           "top":"50%",
           "right":"5px"
            };

Then call the css function before any other functions:

        $(".nav li a:first-child:nth-last-child(2)").css(css).before(function(){


        });

I believe you will need to call the css function before the other functions.

来源：https://stackoverflow.com/questions/27028793/select-pseudo-elements-with-jquery

标签

jquery

css

jquery-selectors

pseudo-element