Welcome to ShenZhenJia Knowledge Sharing Community for programmer and developer-Open, Learning and Share
menu search
person
Welcome To Ask or Share your Answers For Others

Categories

For this question I'm using the following markup:

<body>
    <p>1</p> <!-- Paragraph 1 -->
    <p>2</p> <!-- Paragraph 2 -->
    <p>3</p> <!-- Paragraph 3 -->
</body>

From the Selectors Level 3 specification, the following selector rules apply:

*        any element
E + F    an F element immediately preceded by an E element
E ~ F    an F element preceded by an E element

Based on this, the following should occur:

body + * { } /* Selects nothing as no elements precede body */
body ~ * { } /* As above. */
p + *    { } /* Selects Paragraph 2 and Paragraph 3 as these are preceded by p */
p ~ *    { } /* As above. */
* + *    { } /* As above. */
* ~ *    { } /* As above. */

False!

* + * and * ~ * are somehow able to select Paragraph 1 along with 2 and 3! Paragraph 1 isn't preceded by anything, so should be impossible to access:

body + * { background: #000; }
body ~ * { background: #000; }
p ~ *    { color: #f00; }
p + *    { font-weight: bold; }
* + *    { text-decoration: underline; }
* ~ *    { font-style: italic; }

Result:

Result example; paragraph 2 and 3 are red and all paragraphs are italic and underlined

As you can see, paragraph 1 isn't preceded by the body or a phantom p, yet it is apparently preceded by something. It should have no custom styling applied to it at all, yet is somehow affected by those last two selectors. What is the logic behind this?

JSFiddle example.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
thumb_up_alt 0 like thumb_down_alt 0 dislike
289 views
Welcome To Ask or Share your Answers For Others

1 Answer

* + * Styles any element that is an immediate sibling of any element starting from the document root - Since the <head> is actually an immediate preceding sibling of the body (despite not being visible in your code) this selector targets the body and the last two paragraphs, since the first paragraph isn't immediately following another sibling element. All three paragraphs happened to be underlined due to the nature of text-decoration on block-level descendants in the normal flow.

* ~ * This is basically the same thing as above, except using the general sibling combinator .. it styles downstream sibling element(s) that appear after the <head> regardless of whether they're immediate siblings or not. Since the <body> is the only sibling, this has the same effect as the above selector. The first paragraph is italicized due to inheritance.

p ~ * selects a sibling element that is following a <p> which in your example is the last two paragraphs. p + * styles any element that is immediate sibling of a paragraph, which would also be the last two <p> elements.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
thumb_up_alt 0 like thumb_down_alt 0 dislike
Welcome to ShenZhenJia Knowledge Sharing Community for programmer and developer-Open, Learning and Share
...