102 lines
3.1 KiB
JavaScript
102 lines
3.1 KiB
JavaScript
/*---------------------------------------------------------------------------------------------
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* Copyright (c) Microsoft Corporation. All rights reserved.
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* Licensed under the MIT License. See License.txt in the project root for license information.
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*--------------------------------------------------------------------------------------------*/
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'use strict';
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export function startsWith(haystack, needle) {
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if (haystack.length < needle.length) {
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return false;
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}
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for (let i = 0; i < needle.length; i++) {
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if (haystack[i] !== needle[i]) {
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return false;
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}
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}
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return true;
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}
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/**
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* Determines if haystack ends with needle.
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*/
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export function endsWith(haystack, needle) {
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let diff = haystack.length - needle.length;
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if (diff > 0) {
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return haystack.lastIndexOf(needle) === diff;
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}
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else if (diff === 0) {
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return haystack === needle;
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}
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else {
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return false;
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}
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}
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/**
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* Computes the difference score for two strings. More similar strings have a higher score.
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* We use largest common subsequence dynamic programming approach but penalize in the end for length differences.
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* Strings that have a large length difference will get a bad default score 0.
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* Complexity - both time and space O(first.length * second.length)
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* Dynamic programming LCS computation http://en.wikipedia.org/wiki/Longest_common_subsequence_problem
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*
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* @param first a string
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* @param second a string
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*/
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export function difference(first, second, maxLenDelta = 4) {
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let lengthDifference = Math.abs(first.length - second.length);
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// We only compute score if length of the currentWord and length of entry.name are similar.
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if (lengthDifference > maxLenDelta) {
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return 0;
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}
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// Initialize LCS (largest common subsequence) matrix.
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let LCS = [];
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let zeroArray = [];
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let i, j;
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for (i = 0; i < second.length + 1; ++i) {
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zeroArray.push(0);
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}
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for (i = 0; i < first.length + 1; ++i) {
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LCS.push(zeroArray);
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}
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for (i = 1; i < first.length + 1; ++i) {
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for (j = 1; j < second.length + 1; ++j) {
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if (first[i - 1] === second[j - 1]) {
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LCS[i][j] = LCS[i - 1][j - 1] + 1;
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}
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else {
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LCS[i][j] = Math.max(LCS[i - 1][j], LCS[i][j - 1]);
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}
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}
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}
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return LCS[first.length][second.length] - Math.sqrt(lengthDifference);
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}
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/**
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* Limit of string length.
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*/
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export function getLimitedString(str, ellipsis = true) {
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if (!str) {
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return '';
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}
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if (str.length < 140) {
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return str;
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}
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return str.slice(0, 140) + (ellipsis ? '\u2026' : '');
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}
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/**
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* Limit of string length.
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*/
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export function trim(str, regexp) {
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const m = regexp.exec(str);
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if (m && m[0].length) {
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return str.substr(0, str.length - m[0].length);
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}
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return str;
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}
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export function repeat(value, count) {
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let s = '';
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while (count > 0) {
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if ((count & 1) === 1) {
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s += value;
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}
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value += value;
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count = count >>> 1;
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}
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return s;
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}
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