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Improve performance by reusing precompiled regular expressions #85

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nazar-pc wants to merge 1 commit into from
+15 −6
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Improve performance by reusing precompiled regular expressions #85

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21 changes: 15 additions & 6 deletions index.js
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
'use strict';

const regexp1 = /[\p{Lu}]/u;
const regexp2 = /[\p{Ll}]/u;
const preserveCamelCase = (string, locale) => {
let isLastCharLower = false;
let isLastCharUpper = false;
Expand All @@ -8,13 +10,13 @@ const preserveCamelCase = (string, locale) => {
for (let i = 0; i < string.length; i++) {
const character = string[i];

if (isLastCharLower && /[\p{Lu}]/u.test(character)) {
if (isLastCharLower && regexp1.test(character)) {
string = string.slice(0, i) + '-' + string.slice(i);
isLastCharLower = false;
isLastLastCharUpper = isLastCharUpper;
isLastCharUpper = true;
i++;
} else if (isLastCharUpper && isLastLastCharUpper && /[\p{Ll}]/u.test(character)) {
} else if (isLastCharUpper && isLastLastCharUpper && regexp2.test(character)) {
string = string.slice(0, i - 1) + '-' + string.slice(i - 1);
isLastLastCharUpper = isLastCharUpper;
isLastCharUpper = false;
Expand All @@ -29,15 +31,22 @@ const preserveCamelCase = (string, locale) => {
return string;
};

const regexp3 = /^[\p{Lu}](?![\p{Lu}])/gu;
const preserveConsecutiveUppercase = input => {
return input.replace(/^[\p{Lu}](?![\p{Lu}])/gu, m1 => m1.toLowerCase());
regexp3.lastIndex = 0;
return input.replace(regexp3, m1 => m1.toLowerCase());
};

const regexp4 = /[_.\- ]+([\p{Alpha}\p{N}_]|$)/gu;
const regexp5 = /\d+([\p{Alpha}\p{N}_]|$)/gu;
const postProcess = (input, options) => {
return input.replace(/[_.\- ]+([\p{Alpha}\p{N}_]|$)/gu, (_, p1) => p1.toLocaleUpperCase(options.locale))
.replace(/\d+([\p{Alpha}\p{N}_]|$)/gu, m => m.toLocaleUpperCase(options.locale));
regexp4.lastIndex = 0;
regexp5.lastIndex = 0;
return input.replace(regexp4, (_, p1) => p1.toLocaleUpperCase(options.locale))
.replace(regexp5, m => m.toLocaleUpperCase(options.locale));
};

const regexp6 = /^[_.\- ]+/;
const camelCase = (input, options) => {
if (!(typeof input === 'string' || Array.isArray(input))) {
throw new TypeError('Expected the input to be `string | string[]`');
Expand Down Expand Up @@ -71,7 +80,7 @@ const camelCase = (input, options) => {
input = preserveCamelCase(input, options.locale);
}

input = input.replace(/^[_.\- ]+/, '');
input = input.replace(regexp6, '');

if (options.preserveConsecutiveUppercase) {
input = preserveConsecutiveUppercase(input);
Expand Down