忽略建议属性名是问题。 jQuery API明确声明可以接受任何一种符号： http://api.jquery.com/css/

实际的问题是你在这行上缺少一个大括号：

  $（＃myParagraph）css（{backgroundColor：black，color：white）; 
 

更改为：

  $（＃myParagraph）。css（{backgroundColor：black，color：white}）; 
 

这是一个工作演示： http://jsfiddle.net/YPYz8/

I am trying to change the CSS using jQuery:

$(init);
    
function init() {
    $("h1").css("backgroundColor", "yellow");
    $("#myParagraph").css({"backgroundColor":"black","color":"white");
    $(".bordered").css("border", "1px solid black");
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
<div class="bordered">
    <h1>Header</h1>
    <p id="myParagraph">This is some paragraph text</p>
</div>

What am I missing here?

Ignore the people that are suggesting that the property name is the issue. The jQuery API explicitly states that either notation is acceptable: http://api.jquery.com/css/

The actual problem is that you are missing a close curly brace on this line:

$("#myParagraph").css({"backgroundColor":"black","color":"white");

Change it to this:

$("#myParagraph").css({"backgroundColor": "black", "color": "white"});

Here's a working demo: http://jsfiddle.net/YPYz8/