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139 lines
3.7 KiB
139 lines
3.7 KiB
'use strict'; |
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Object.defineProperty(exports, '__esModule', { |
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value: true, |
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}); |
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exports.suggestionList = suggestionList; |
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var _naturalCompare = require('./naturalCompare.js'); |
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/** |
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* Given an invalid input string and a list of valid options, returns a filtered |
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* list of valid options sorted based on their similarity with the input. |
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*/ |
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function suggestionList(input, options) { |
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const optionsByDistance = Object.create(null); |
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const lexicalDistance = new LexicalDistance(input); |
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const threshold = Math.floor(input.length * 0.4) + 1; |
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for (const option of options) { |
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const distance = lexicalDistance.measure(option, threshold); |
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if (distance !== undefined) { |
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optionsByDistance[option] = distance; |
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} |
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} |
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return Object.keys(optionsByDistance).sort((a, b) => { |
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const distanceDiff = optionsByDistance[a] - optionsByDistance[b]; |
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return distanceDiff !== 0 |
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? distanceDiff |
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: (0, _naturalCompare.naturalCompare)(a, b); |
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}); |
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} |
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/** |
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* Computes the lexical distance between strings A and B. |
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* |
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* The "distance" between two strings is given by counting the minimum number |
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* of edits needed to transform string A into string B. An edit can be an |
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* insertion, deletion, or substitution of a single character, or a swap of two |
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* adjacent characters. |
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* |
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* Includes a custom alteration from Damerau-Levenshtein to treat case changes |
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* as a single edit which helps identify mis-cased values with an edit distance |
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* of 1. |
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* |
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* This distance can be useful for detecting typos in input or sorting |
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*/ |
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class LexicalDistance { |
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constructor(input) { |
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this._input = input; |
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this._inputLowerCase = input.toLowerCase(); |
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this._inputArray = stringToArray(this._inputLowerCase); |
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this._rows = [ |
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new Array(input.length + 1).fill(0), |
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new Array(input.length + 1).fill(0), |
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new Array(input.length + 1).fill(0), |
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]; |
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} |
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measure(option, threshold) { |
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if (this._input === option) { |
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return 0; |
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} |
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const optionLowerCase = option.toLowerCase(); // Any case change counts as a single edit |
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if (this._inputLowerCase === optionLowerCase) { |
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return 1; |
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} |
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let a = stringToArray(optionLowerCase); |
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let b = this._inputArray; |
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if (a.length < b.length) { |
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const tmp = a; |
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a = b; |
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b = tmp; |
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} |
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const aLength = a.length; |
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const bLength = b.length; |
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if (aLength - bLength > threshold) { |
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return undefined; |
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} |
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const rows = this._rows; |
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for (let j = 0; j <= bLength; j++) { |
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rows[0][j] = j; |
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} |
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for (let i = 1; i <= aLength; i++) { |
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const upRow = rows[(i - 1) % 3]; |
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const currentRow = rows[i % 3]; |
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let smallestCell = (currentRow[0] = i); |
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for (let j = 1; j <= bLength; j++) { |
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const cost = a[i - 1] === b[j - 1] ? 0 : 1; |
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let currentCell = Math.min( |
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upRow[j] + 1, // delete |
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currentRow[j - 1] + 1, // insert |
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upRow[j - 1] + cost, // substitute |
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); |
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if (i > 1 && j > 1 && a[i - 1] === b[j - 2] && a[i - 2] === b[j - 1]) { |
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// transposition |
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const doubleDiagonalCell = rows[(i - 2) % 3][j - 2]; |
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currentCell = Math.min(currentCell, doubleDiagonalCell + 1); |
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} |
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if (currentCell < smallestCell) { |
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smallestCell = currentCell; |
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} |
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currentRow[j] = currentCell; |
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} // Early exit, since distance can't go smaller than smallest element of the previous row. |
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if (smallestCell > threshold) { |
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return undefined; |
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} |
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} |
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const distance = rows[aLength % 3][bLength]; |
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return distance <= threshold ? distance : undefined; |
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} |
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} |
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function stringToArray(str) { |
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const strLength = str.length; |
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const array = new Array(strLength); |
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for (let i = 0; i < strLength; ++i) { |
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array[i] = str.charCodeAt(i); |
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} |
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return array; |
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}
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