CSS Pseudo Element Counters: can you increment an alphabet letter “a”, “b”, “c”, etc instead of a number?

问题

As defined here:

http://www.w3.org/TR/CSS21/generate.html#propdef-counter-increment

You can use code like the following to increment numbers in pseudo elements.

H1:before {
    content: "Chapter " counter(chapter) ". ";
    counter-increment: chapter;  /* Add 1 to chapter */
}
H1 {
    counter-reset: section;      /* Set section to 0 */
}
H2:before {
    content: counter(chapter) "." counter(section) " ";
    counter-increment: section;
}

Is there a way you can use the same code to increment letters like "a", "b", "c", etc?

Thank you!

回答1:

Yes, the second argument to counter() defines the type of counter used, as for the list-style-type from a regular ul or ol; for example:

content: counter(chapter, lower-alpha);

ul {
  counter-reset: listStyle;
}
ul li {
  margin-left: 1em;
  counter-increment: listStyle;
}
ul li::before {
  margin-right: 1em;
  content: counter(listStyle, lower-alpha);
}

<ul>
  <li>one</li>
  <li>two</li>
  <li>three</li>
</ul>

JS Fiddle demo.

Others include: decimal, decimal-leading-zero, lower-roman, upper-roman, lower-greek, lower-latin, upper-latin, armenian, georgian, lower-alpha, upper-alpha.

As there seems to have been something of an update to the above list of styles, I chose to add a code snippet which allows the user to choose from the (currently-) available options, along with an 'output' area, to show how to use that style with CSS generated-content:

let select = document.querySelector('select'),
  output = document.querySelector('#currentCounter'),
  changeEvent = new Event('change');

select.addEventListener('change', function() {
  document.body.style.setProperty('--listStyleType', this.value);
  output.textContent = this.value;
});

select.dispatchEvent(changeEvent);

body {
  --listStyleType: decimal;
}

ul {
  counter-reset: listStyle;
  columns: 2;
  margin-top: 0.5em;
  list-style-type: none;
}

ul li {
  counter-increment: listStyle;
}

ul li::before {
  content: counter(listStyle, var(--listStyleType));
  display: inline-block;
  margin-right: 0.5em;
  width: 1.5em;
  height: 1.5em;
  line-height: 2em;
  text-align: center;
}

code {
  display: block;
  white-space: pre-wrap;
  width: 80%;
  box-sizing: border-box;
  margin: 1em auto;
  padding: 0.5em;
  box-shadow: 0 0 0 3px limegreen;
}

code::after {
  content: '\A';
}

#currentCounter {
  color: #f90;
}

<label for="counterChoice">Please select a CSS counter:</label>
<select id="counterChoice">
  <option value="arabic-indic">arabic-indic</option>
  <option value="armenian">armenian</option>
  <option value="bengali">bengali</option>
  <option value="cambodian">cambodian</option>
  <option value="circle">circle</option>
  <option value="cjk-decimal">cjk-decimal</option>
  <option value="cjk-earthly-branch">cjk-earthly-branch</option>
  <option value="cjk-heavenly-stem">cjk-heavenly-stem</option>
  <option value="decimal">decimal</option>
  <option value="decimal-leading-zero">decimal-leading-zero</option>
  <option value="devanagari">devanagari</option>
  <option value="disc">disc</option>
  <option value="disclosure-closed">disclosure-closed</option>
  <option value="disclosure-open">disclosure-open</option>
  <option value="ethiopic-numeric">ethiopic-numeric</option>
  <option value="georgian">georgian</option>
  <option value="gujarati">gujarati</option>
  <option value="gurmukhi">gurmukhi</option>
  <option value="hebrew">hebrew</option>
  <option value="hiragana">hiragana</option>
  <option value="hiragana-iroha">hiragana-iroha</option>
  <option value="japanese-formal">japanese-formal</option>
  <option value="japanese-informal">japanese-informal</option>
  <option value="kannada">kannada</option>
  <option value="katakana">katakana</option>
  <option value="katakana-iroha">katakana-iroha</option>
  <option value="khmer">khmer</option>
  <option value="korean-hangul-formal">korean-hangul-formal</option>
  <option value="korean-hanja-formal">korean-hanja-formal</option>
  <option value="korean-hanja-informal">korean-hanja-informal</option>
  <option value="lao">lao</option>
  <option value="lower-alpha">lower-alpha</option>
  <option value="lower-alpha">lower-alpha</option>
  <option value="lower-armenian">lower-armenian</option>
  <option value="lower-greek">lower-greek</option>
  <option value="lower-latin">lower-latin</option>
  <option value="lower-roman">lower-roman</option>
  <option value="malayalam">malayalam</option>
  <option value="mongolian">mongolian</option>
  <option value="myanmar">myanmar</option>
  <option value="oriya">oriya</option>
  <option value="persian">persian</option>
  <option value="simp-chinese-formal">simp-chinese-formal</option>
  <option value="simp-chinese-informal">simp-chinese-informal</option>
  <option value="square">square</option>
  <option value="tamil">tamil</option>
  <option value="telugu">telugu</option>
  <option value="thai">thai</option>
  <option value="tibetan">tibetan</option>
  <option value="trad-chinese-formal">trad-chinese-formal</option>
  <option value="trad-chinese-informal">trad-chinese-informal</option>
  <option value="upper-alpha">upper-alpha</option>
  <option value="upper-armenian">upper-armenian</option>
  <option value="upper-latin">upper-latin</option>
  <option value="upper-roman">upper-roman</option>
</select>
<ul>
  <li>one</li>
  <li>two</li>
  <li>three</li>
  <li>four</li>
  <li>five</li>
  <li>six</li>
  <li>seven</li>
  <li>eight</li>
  <li>nine</li>
  <li>ten</li>
</ul>

<code>
  li::before {
    content: counter(&lt;counterName&gt;, <span id="currentCounter"></span>)
  }
</code>

The currently-available (as of 2017-02-27):

arabic-indic
armenian
bengali
cambodian
circle
cjk-decimal
cjk-earthly-branch
cjk-heavenly-stem
decimal
decimal-leading-zero
devanagari
disc
disclosure-closed
disclosure-open
ethiopic-numeric
georgian
gujarati
gurmukhi
hebrew
hiragana
hiragana-iroha
japanese-formal
japanese-informal
kannada
katakana
katakana-iroha
khmer
korean-hangul-formal
korean-hanja-formal
korean-hanja-informal
lao
lower-alpha
lower-alpha
lower-armenian
lower-greek
lower-latin
lower-roman
malayalam
mongolian
myanmar
oriya
persian
simp-chinese-formal
simp-chinese-informal
square
tamil
telugu
thai
tibetan
trad-chinese-formal
trad-chinese-informal
upper-alpha
upper-armenian
upper-latin
upper-roman

References:

list-style-type.
"Generated Content, automatic numbering and lists," from the W3 (now outdated).
"CSS Counter Styles, Level 3," from the W3.

来源：https://stackoverflow.com/questions/16943805/css-pseudo-element-counters-can-you-increment-an-alphabet-letter-a-b-c

标签

css

pseudo-element

css-content