[id ^ = product] 
 

$ b b

^ = 表示开头为。相反， $ = 表示结束于。

符号实际上是从Regex语法借用的，其中 ^ 和 $ 分别表示字符串开始和字符串结束。

请参阅规格了解完整信息。

If the HTML has elements like this:

id="product42"
id="product43"
...

How do I match all of those id's starting with "product"?

I've seen answers that do this exactly using javascript, but how to do it with only CSS?

[id^=product]

^= indicates "starts with". Conversely, $= indicates "ends with".

The symbols are actually borrowed from Regex syntax, where ^ and $ mean "start of string" and "end of string" respectively.

See the specs for full information.