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- // Calculate the specificity for a selector by dividing it into simple selectors and counting them
- var calculate = function(input) {
- var selectors,
- selector,
- i,
- len,
- results = [];
-
- // Separate input by commas
- selectors = input.split(',');
-
- for (i = 0, len = selectors.length; i < len; i += 1) {
- selector = selectors[i];
- if (selector.length > 0) {
- results.push(calculateSingle(selector));
- }
- }
-
- return results;
- };
-
- /**
- * Calculates the specificity of CSS selectors
- * http://www.w3.org/TR/css3-selectors/#specificity
- *
- * Returns an object with the following properties:
- * - selector: the input
- * - specificity: e.g. 0,1,0,0
- * - parts: array with details about each part of the selector that counts towards the specificity
- * - specificityArray: e.g. [0, 1, 0, 0]
- */
- var calculateSingle = function(input) {
- var selector = input,
- findMatch,
- typeCount = {
- 'a': 0,
- 'b': 0,
- 'c': 0
- },
- parts = [],
- // The following regular expressions assume that selectors matching the preceding regular expressions have been removed
- attributeRegex = /(\[[^\]]+\])/g,
- idRegex = /(#[^\#\s\+>~\.\[:\)]+)/g,
- classRegex = /(\.[^\s\+>~\.\[:\)]+)/g,
- pseudoElementRegex = /(::[^\s\+>~\.\[:]+|:first-line|:first-letter|:before|:after)/gi,
- // A regex for pseudo classes with brackets - :nth-child(), :nth-last-child(), :nth-of-type(), :nth-last-type(), :lang()
- // The negation psuedo class (:not) is filtered out because specificity is calculated on its argument
- // :global and :local are filtered out - they look like psuedo classes but are an identifier for CSS Modules
- pseudoClassWithBracketsRegex = /(:(?!not|global|local)[\w-]+\([^\)]*\))/gi,
- // A regex for other pseudo classes, which don't have brackets
- pseudoClassRegex = /(:(?!not|global|local)[^\s\+>~\.\[:]+)/g,
- elementRegex = /([^\s\+>~\.\[:]+)/g;
-
- // Find matches for a regular expression in a string and push their details to parts
- // Type is "a" for IDs, "b" for classes, attributes and pseudo-classes and "c" for elements and pseudo-elements
- findMatch = function(regex, type) {
- var matches, i, len, match, index, length;
- if (regex.test(selector)) {
- matches = selector.match(regex);
- for (i = 0, len = matches.length; i < len; i += 1) {
- typeCount[type] += 1;
- match = matches[i];
- index = selector.indexOf(match);
- length = match.length;
- parts.push({
- selector: input.substr(index, length),
- type: type,
- index: index,
- length: length
- });
- // Replace this simple selector with whitespace so it won't be counted in further simple selectors
- selector = selector.replace(match, Array(length + 1).join(' '));
- }
- }
- };
-
- // Replace escaped characters with plain text, using the "A" character
- // https://www.w3.org/TR/CSS21/syndata.html#characters
- (function() {
- var replaceWithPlainText = function(regex) {
- var matches, i, len, match;
- if (regex.test(selector)) {
- matches = selector.match(regex);
- for (i = 0, len = matches.length; i < len; i += 1) {
- match = matches[i];
- selector = selector.replace(match, Array(match.length + 1).join('A'));
- }
- }
- },
- // Matches a backslash followed by six hexadecimal digits followed by an optional single whitespace character
- escapeHexadecimalRegex = /\\[0-9A-Fa-f]{6}\s?/g,
- // Matches a backslash followed by fewer than six hexadecimal digits followed by a mandatory single whitespace character
- escapeHexadecimalRegex2 = /\\[0-9A-Fa-f]{1,5}\s/g,
- // Matches a backslash followed by any character
- escapeSpecialCharacter = /\\./g;
-
- replaceWithPlainText(escapeHexadecimalRegex);
- replaceWithPlainText(escapeHexadecimalRegex2);
- replaceWithPlainText(escapeSpecialCharacter);
- }());
-
- // Remove anything after a left brace in case a user has pasted in a rule, not just a selector
- (function() {
- var regex = /{[^]*/gm,
- matches, i, len, match;
- if (regex.test(selector)) {
- matches = selector.match(regex);
- for (i = 0, len = matches.length; i < len; i += 1) {
- match = matches[i];
- selector = selector.replace(match, Array(match.length + 1).join(' '));
- }
- }
- }());
-
- // Add attribute selectors to parts collection (type b)
- findMatch(attributeRegex, 'b');
-
- // Add ID selectors to parts collection (type a)
- findMatch(idRegex, 'a');
-
- // Add class selectors to parts collection (type b)
- findMatch(classRegex, 'b');
-
- // Add pseudo-element selectors to parts collection (type c)
- findMatch(pseudoElementRegex, 'c');
-
- // Add pseudo-class selectors to parts collection (type b)
- findMatch(pseudoClassWithBracketsRegex, 'b');
- findMatch(pseudoClassRegex, 'b');
-
- // Remove universal selector and separator characters
- selector = selector.replace(/[\*\s\+>~]/g, ' ');
-
- // Remove any stray dots or hashes which aren't attached to words
- // These may be present if the user is live-editing this selector
- selector = selector.replace(/[#\.]/g, ' ');
-
- // Remove the negation psuedo-class (:not) but leave its argument because specificity is calculated on its argument
- // Remove non-standard :local and :global CSS Module identifiers because they do not effect the specificity
- selector = selector.replace(/:not/g, ' ');
- selector = selector.replace(/:local/g, ' ');
- selector = selector.replace(/:global/g, ' ');
- selector = selector.replace(/[\(\)]/g, ' ');
-
- // The only things left should be element selectors (type c)
- findMatch(elementRegex, 'c');
-
- // Order the parts in the order they appear in the original selector
- // This is neater for external apps to deal with
- parts.sort(function(a, b) {
- return a.index - b.index;
- });
-
- return {
- selector: input,
- specificity: '0,' + typeCount.a.toString() + ',' + typeCount.b.toString() + ',' + typeCount.c.toString(),
- specificityArray: [0, typeCount.a, typeCount.b, typeCount.c],
- parts: parts
- };
- };
-
- /**
- * Compares two CSS selectors for specificity
- * Alternatively you can replace one of the CSS selectors with a specificity array
- *
- * - it returns -1 if a has a lower specificity than b
- * - it returns 1 if a has a higher specificity than b
- * - it returns 0 if a has the same specificity than b
- */
- var compare = function(a, b) {
- var aSpecificity,
- bSpecificity,
- i;
-
- if (typeof a ==='string') {
- if (a.indexOf(',') !== -1) {
- throw 'Invalid CSS selector';
- } else {
- aSpecificity = calculateSingle(a)['specificityArray'];
- }
- } else if (Array.isArray(a)) {
- if (a.filter(function(e) { return (typeof e === 'number'); }).length !== 4) {
- throw 'Invalid specificity array';
- } else {
- aSpecificity = a;
- }
- } else {
- throw 'Invalid CSS selector or specificity array';
- }
-
- if (typeof b ==='string') {
- if (b.indexOf(',') !== -1) {
- throw 'Invalid CSS selector';
- } else {
- bSpecificity = calculateSingle(b)['specificityArray'];
- }
- } else if (Array.isArray(b)) {
- if (b.filter(function(e) { return (typeof e === 'number'); }).length !== 4) {
- throw 'Invalid specificity array';
- } else {
- bSpecificity = b;
- }
- } else {
- throw 'Invalid CSS selector or specificity array';
- }
-
- for (i = 0; i < 4; i += 1) {
- if (aSpecificity[i] < bSpecificity[i]) {
- return -1;
- } else if (aSpecificity[i] > bSpecificity[i]) {
- return 1;
- }
- }
-
- return 0;
- };
-
- export { calculate, compare };
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