简短版2017年4月12日
挑战者出现。
(Note: 保留了HTML标签)
var getMatchedCSSRules = (el, css = el.ownerDocument.styleSheets) =>
[].concat(...[...css].map(s => [...s.cssRules||[]]))
.filter(r => el.matches(r.selectorText));
代码中的第一行/* 1 */
创建了一个扁平数组包含所有规则。
第二行/* 2 */
将不匹配的规则丢弃。
该方法基于同一页面上@S.B.的函数css(el)
。
示例1
var div = iframedoc.querySelector("#myelement");
var rules = getMatchedCSSRules(div, iframedoc.styleSheets);
console.log(rules[0].parentStyleSheet.ownerNode, rules[0].cssText);
示例2
var getMatchedCSSRules = (el, css = el.ownerDocument.styleSheets) =>
[].concat(...[...css].map(s => [...s.cssRules||[]]))
.filter(r => el.matches(r.selectorText));
function Go(big,show) {
var r = getMatchedCSSRules(big);
PrintInfo:
var f = (dd,rr,ee="\n") => dd + rr.cssText.slice(0,50) + ee;
show.value += "--------------- Rules: ----------------\n";
show.value += f("Rule 1: ", r[0]);
show.value += f("Rule 2: ", r[1]);
show.value += f("Inline: ", big.style);
show.value += f("Computed: ", getComputedStyle(big), "(…)\n");
show.value += "-------- Style element (HTML): --------\n";
show.value += r[0].parentStyleSheet.ownerNode.outerHTML;
}
Go(...document.querySelectorAll("#big,#show"));
.red {color: red;}
#big {font-size: 20px;}
<h3 id="big" class="red" style="margin: 0">Lorem ipsum</h3>
<textarea id="show" cols="70" rows="10"></textarea>
缺点
- 没有媒体处理,没有
@import
,@media
。
- 无法访问从跨域样式表加载的样式。
- 不能按选择器“特异性”(重要性顺序)排序。
- 没有从父级继承的样式。
- 可能无法使用旧版或基本浏览器。
- 不确定它如何处理伪类和伪选择器,但似乎还可以。
也许有一天我会解决这些缺点。
长版本2018年8月12日
这是一个来自某人的GitHub页面的更全面的实现(从这个原始代码进行fork,经由Bugzilla)。为Gecko和IE编写,但据传也能与Blink一起工作。
2017年5月4日:特异性计算器存在关键错误,现已修复。(我无法通知作者,因为我没有GitHub帐户。)
2018年8月12日:最近的Chrome更新似乎已将对象范围(this
)与分配给独立变量的方法分离。因此,调用matcher(selector)
停止工作。通过将其替换为matcher.call(el, selector)
来解决。
if (typeof window.getMatchedCSSRules !== 'function') {
var ELEMENT_RE = /[\w-]+/g,
ID_RE = /#[\w-]+/g,
CLASS_RE = /\.[\w-]+/g,
ATTR_RE = /\[[^\]]+\]/g,
PSEUDO_CLASSES_RE = /\:(?!not)[\w-]+(\(.*\))?/g,
PSEUDO_ELEMENTS_RE = /\:\:?(after|before|first-letter|first-line|selection)/g;
function toArray(list) {
return [].slice.call(list);
}
function getSheetRules(stylesheet) {
var sheet_media = stylesheet.media && stylesheet.media.mediaText;
if ( stylesheet.disabled ) return [];
if ( sheet_media && sheet_media.length && ! window.matchMedia(sheet_media).matches ) return [];
return toArray(stylesheet.cssRules);
}
function _find(string, re) {
var matches = string.match(re);
return matches ? matches.length : 0;
}
function calculateScore(selector) {
var score = [0,0,0],
parts = selector.split(' '),
part, match;
while (part = parts.shift(), typeof part == 'string') {
match = _find(part, PSEUDO_ELEMENTS_RE);
score[2] += match;
match && (part = part.replace(PSEUDO_ELEMENTS_RE, ''));
match = _find(part, PSEUDO_CLASSES_RE);
score[1] += match;
match && (part = part.replace(PSEUDO_CLASSES_RE, ''));
match = _find(part, ATTR_RE);
score[1] += match;
match && (part = part.replace(ATTR_RE, ''));
match = _find(part, ID_RE);
score[0] += match;
match && (part = part.replace(ID_RE, ''));
match = _find(part, CLASS_RE);
score[1] += match;
match && (part = part.replace(CLASS_RE, ''));
score[2] += _find(part, ELEMENT_RE);
}
return parseInt(score.join(''), 10);
}
function getSpecificityScore(element, selector_text) {
var selectors = selector_text.split(','),
selector, score, result = 0;
while (selector = selectors.shift()) {
if (matchesSelector(element, selector)) {
score = calculateScore(selector);
result = score > result ? score : result;
}
}
return result;
}
function sortBySpecificity(element, rules) {
function compareSpecificity (a, b) {
return getSpecificityScore(element, b.selectorText) - getSpecificityScore(element, a.selectorText);
}
return rules.sort(compareSpecificity);
}
function matchesSelector(el, selector) {
var matcher = el.matchesSelector || el.mozMatchesSelector ||
el.webkitMatchesSelector || el.oMatchesSelector || el.msMatchesSelector;
return matcher.call(el, selector);
}
window.getMatchedCSSRules = function (element ) {
var style_sheets, sheet, sheet_media,
rules, rule,
result = [];
style_sheets = toArray(window.document.styleSheets);
while (sheet = style_sheets.shift()) {
rules = getSheetRules(sheet);
while (rule = rules.shift()) {
if (rule.styleSheet) {
rules = getSheetRules(rule.styleSheet).concat(rules);
continue;
}
else if (rule.media) {
rules = getSheetRules(rule).concat(rules);
continue
}
if (matchesSelector(element, rule.selectorText)) {
result.push(rule);
}
}
}
return sortBySpecificity(element, result);
};
}
已解决的问题
= 匹配
→ += 匹配
return re ? re.length : 0;
→ return matches ? matches.length : 0;
_matchesSelector(element, selector)
→ matchesSelector(element, selector)
matcher(selector)
→ matcher.call(el, selector)