69 lines
1.8 KiB
JavaScript
69 lines
1.8 KiB
JavaScript
const escape = require('sql-escape');
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// http://stackoverflow.com/questions/11919065/sort-an-array-by-the-levenshtein-distance-with-best-performance-in-javascript
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function LevenshteinDistance(s, t) {
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const d = []; // 2d matrix
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// Step 1
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const n = s.length;
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const m = t.length;
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if (n === 0) return m;
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if (m === 0) return n;
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// Create an array of arrays in javascript (a descending loop is quicker)
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for (let i = n; i >= 0; i--) d[i] = [];
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// Step 2
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for (let i = n; i >= 0; i--) d[i][0] = i;
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for (let j = m; j >= 0; j--) d[0][j] = j;
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// Step 3
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for (let i = 1; i <= n; i++) {
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const si = s.charAt(i - 1);
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// Step 4
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for (let j = 1; j <= m; j++) {
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// Check the jagged ld total so far
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if (i === j && d[i][j] > 4) return n;
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const tj = t.charAt(j - 1);
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const cost = (si === tj) ? 0 : 1; // Step 5
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// Calculate the minimum
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let mi = d[i - 1][j] + 1;
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const b = d[i][j - 1] + 1;
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const c = d[i - 1][j - 1] + cost;
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if (b < mi) mi = b;
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if (c < mi) mi = c;
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d[i][j] = mi; // Step 6
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// Damerau transposition
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if (i > 1 && j > 1 && si === t.charAt(j - 2) && s.charAt(i - 2) === tj) {
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d[i][j] = Math.min(d[i][j], d[i - 2][j - 2] + cost);
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}
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}
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}
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// Step 7
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return d[n][m];
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}
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// TODO: get this working properly
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function SanatiseQuery(query) {
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query = query.trim();
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query = query.replace(/[^a-zA-Z0-9,/\s]/g, '');
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query = escape(query);
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query = query.toLowerCase();
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return query;
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}
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module.exports = {
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SanatiseQuery,
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LevenshteinDistance,
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ResultsPerPage: 16,
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};
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