136 lines
3.8 KiB
JavaScript
136 lines
3.8 KiB
JavaScript
(function() {
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'use strict';
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var collator;
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try {
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collator = (typeof Intl !== "undefined" && typeof Intl.Collator !== "undefined") ? Intl.Collator("generic", { sensitivity: "base" }) : null;
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} catch (err){
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console.log("Collator could not be initialized and wouldn't be used");
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}
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// arrays to re-use
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var prevRow = [],
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str2Char = [];
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/**
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* Based on the algorithm at http://en.wikipedia.org/wiki/Levenshtein_distance.
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*/
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var Levenshtein = {
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/**
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* Calculate levenshtein distance of the two strings.
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*
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* @param str1 String the first string.
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* @param str2 String the second string.
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* @param [options] Additional options.
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* @param [options.useCollator] Use `Intl.Collator` for locale-sensitive string comparison.
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* @return Integer the levenshtein distance (0 and above).
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*/
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get: function(str1, str2, options) {
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var useCollator = (options && collator && options.useCollator);
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var str1Len = str1.length,
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str2Len = str2.length;
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// base cases
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if (str1Len === 0) return str2Len;
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if (str2Len === 0) return str1Len;
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// two rows
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var curCol, nextCol, i, j, tmp;
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// initialise previous row
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for (i=0; i<str2Len; ++i) {
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prevRow[i] = i;
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str2Char[i] = str2.charCodeAt(i);
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}
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prevRow[str2Len] = str2Len;
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var strCmp;
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if (useCollator) {
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// calculate current row distance from previous row using collator
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for (i = 0; i < str1Len; ++i) {
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nextCol = i + 1;
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for (j = 0; j < str2Len; ++j) {
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curCol = nextCol;
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// substution
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strCmp = 0 === collator.compare(str1.charAt(i), String.fromCharCode(str2Char[j]));
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nextCol = prevRow[j] + (strCmp ? 0 : 1);
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// insertion
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tmp = curCol + 1;
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if (nextCol > tmp) {
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nextCol = tmp;
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}
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// deletion
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tmp = prevRow[j + 1] + 1;
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if (nextCol > tmp) {
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nextCol = tmp;
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}
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// copy current col value into previous (in preparation for next iteration)
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prevRow[j] = curCol;
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}
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// copy last col value into previous (in preparation for next iteration)
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prevRow[j] = nextCol;
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}
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}
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else {
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// calculate current row distance from previous row without collator
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for (i = 0; i < str1Len; ++i) {
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nextCol = i + 1;
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for (j = 0; j < str2Len; ++j) {
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curCol = nextCol;
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// substution
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strCmp = str1.charCodeAt(i) === str2Char[j];
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nextCol = prevRow[j] + (strCmp ? 0 : 1);
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// insertion
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tmp = curCol + 1;
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if (nextCol > tmp) {
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nextCol = tmp;
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}
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// deletion
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tmp = prevRow[j + 1] + 1;
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if (nextCol > tmp) {
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nextCol = tmp;
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}
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// copy current col value into previous (in preparation for next iteration)
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prevRow[j] = curCol;
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}
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// copy last col value into previous (in preparation for next iteration)
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prevRow[j] = nextCol;
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}
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}
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return nextCol;
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}
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};
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// amd
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if (typeof define !== "undefined" && define !== null && define.amd) {
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define(function() {
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return Levenshtein;
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});
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}
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// commonjs
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else if (typeof module !== "undefined" && module !== null && typeof exports !== "undefined" && module.exports === exports) {
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module.exports = Levenshtein;
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}
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// web worker
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else if (typeof self !== "undefined" && typeof self.postMessage === 'function' && typeof self.importScripts === 'function') {
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self.Levenshtein = Levenshtein;
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}
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// browser main thread
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else if (typeof window !== "undefined" && window !== null) {
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window.Levenshtein = Levenshtein;
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}
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}());
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