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