Initial commit

.gitignore

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+node_modules
+package-lock.json

.prettierrc

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+{
+  "useTabs": false,
+  "tabWidth": 2,
+  "printWidth": 100,
+  "singleQuote": true,
+  "semi": false,
+  "arrowParens": "avoid",
+  "bracketSpacing": true
+}

LICENSE

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+MIT License
+
+Copyright (c) 2020-present Max Kanaradze
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# swap-char
+
+Swaps two chars in a string by indexes.
+
+[![License][license-image]][license-url] [![Downloads][downloads-image]][downloads-url]
+
+## Install
+
+Install using [npm](https://www.npmjs.com/):
+
+```sh
+npm install --save swap-char
+```
+
+or using [yarn](https://yarnpkg.com/)
+
+```sh
+yarn add swap-char
+```
+
+## API
+
+### swapChar(str: string, from: number, to: number)
+
+Swaps chars on `from` and `to` indexes and returns a new string.
+
+**`str: string`**
+
+A string to perform a char swap on.
+
+**`from: number`**
+
+The zero-based index from where to take a char. If negative, it is treated as `str.length + from`. (For example, if `from` is `-3` it is treated as `str.length - 3`).
+
+If `from` is greater than or equal to `str.length`, `swapChar()` returns `str` without any changes.
+
+**`to: number`**
+
+The zero-based index at which to put a char. If negative, it is treated as `str.length + to`. (For example, if `to` is `-3` it is treated as `str.length - 3`).
+
+If `to` is greater than or equal to `str.length`, `swapChar()` returns `str` without any changes.
+
+## Examples
+
+```js
+import swapChar from 'swap-char';
+
+swapChar('abc', 0, 1); // <~ 'bac'
+swapChar('abc', 2, 0); // <~ 'cba'
+
+// with negative indexes
+swapChar('abc', 0, -1); // <~ 'cba'
+swapChar('abc', -2, -1); // <~ 'acb'
+
+// with incorrect indexes - returns the same string
+swapChar('abc', 50, 0); // <~ 'abc'
+swapChar('abc', 2, Infinity); // <~ 'abc'
+
+```
+
+#### Author
+
+**Max Kanaradze**
+
+[GitHub Profile](https://github.com/null096)
+
+#### MIT Licensed
+
+[license-image]: http://img.shields.io/npm/l/swap-char.svg
+[license-url]: LICENSE
+
+[downloads-image]: https://img.shields.io/npm/dm/swap-char
+[downloads-url]: http://npm-stat.com/charts.html?package=swap-char

index.d.ts

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+declare module 'swap-char' {
+  const swapChar: (str: string, from: number, to: number) => string
+  export default swapChar
+}

index.js

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+function isValidIndex(index, strLength) {
+  return index >= 0 && index < strLength && !isNaN(index) && isFinite(index)
+}
+
+function swapChar(str, from, to) {
+  if (str === undefined || str === null) {
+    return ''
+  }
+
+  str = String(str)
+  from = Math.floor(from)
+  to = Math.floor(to)
+  const strLength = str.length
+  if (from < 0) {
+    from = strLength + from
+  }
+  if (to < 0) {
+    to = strLength + to
+  }
+
+  if (!isValidIndex(from, strLength) || !isValidIndex(to, strLength)) {
+    return str
+  }
+
+  if (from === to) {
+    return str
+  }
+  const min = Math.min(from, to)
+  const max = Math.max(from, to)
+  // prettier-ignore
+  const newStr =
+      str.slice(0, min) +
+      str[max] +
+      str.slice(min + 1, max) +
+      str[min] +
+      str.slice(max + 1)
+  return newStr
+}
+
+module.exports = swapChar

package.json

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+{
+  "name": "swap-char",
+  "version": "1.0.0",
+  "description": "Swaps two chars in a string by indexes",
+  "main": "./index.js",
+  "types": "./index.d.ts",
+  "scripts": {
+    "test": "ava",
+    "test:watch": "ava --watch",
+    "prepublishOnly": "npm run test"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/null096/swap-char.git"
+  },
+  "files": [
+    "index.js",
+    "index.d.ts"
+  ],
+  "keywords": [
+    "swap",
+    "char",
+    "string",
+    "index",
+    "indexes"
+  ],
+  "author": "Max Kanaradze",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/null096/swap-char/issues"
+  },
+  "homepage": "https://github.com/null096/swap-char#readme",
+  "devDependencies": {
+    "ava": "^3.12.1"
+  }
+}

test.js

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+const test = require('ava')
+const swapChar = require('./index')
+
+test('Should swap two chars in a string', t => {
+  t.is(swapChar('123', 0, 0), '123')
+  t.is(swapChar('123', 0, 1), '213')
+  t.is(swapChar('123', 0, 2), '321')
+  t.is(swapChar('123', 1, 0), '213')
+  t.is(swapChar('123', 1, 1), '123')
+  t.is(swapChar('123', 1, 2), '132')
+  t.is(swapChar('123', 2, 0), '321')
+  t.is(swapChar('123', 2, 1), '132')
+  t.is(swapChar('123', 2, 2), '123')
+})
+
+test('Should swap two chars in a string with negative indexes', t => {
+  t.is(swapChar('123', -1, 0), '321')
+  t.is(swapChar('123', -1, 1), '132')
+  t.is(swapChar('123', -1, 2), '123')
+  t.is(swapChar('123', -2, 0), '213')
+  t.is(swapChar('123', -2, 1), '123')
+  t.is(swapChar('123', -2, 2), '132')
+  t.is(swapChar('123', -3, 0), '123')
+  t.is(swapChar('123', -3, 1), '213')
+  t.is(swapChar('123', -3, 2), '321')
+
+  t.is(swapChar('123', 0, -1), '321')
+  t.is(swapChar('123', 1, -1), '132')
+  t.is(swapChar('123', 2, -3), '321')
+
+  t.is(swapChar('123', -2, -1), '132')
+  t.is(swapChar('123', -3, -2), '213')
+  t.is(swapChar('123', -1, -3), '321')
+})
+
+test('Shoud handle edge cases properly', t => {
+  t.is(swapChar('123', 5, 0), '123')
+  t.is(swapChar('123', 0, 5), '123')
+  t.is(swapChar('123', 5, 999), '123')
+  t.is(swapChar('123', -99, -99), '123')
+  t.throws(() => swapChar('123', Symbol(1), 0))
+  t.is(swapChar([1, 2], 0, 1), ',12')
+  t.is(swapChar('123', null, undefined), '123')
+  t.is(swapChar('123', '1', '2'), '132')
+  t.is(swapChar('123', 0.5, -1), '321')
+  t.is(swapChar('123', /test/, -1), '123')
+  t.is(swapChar('123', '', ''), '123')
+  t.is(swapChar('123', '-1', '-2'), '132')
+  t.is(swapChar('123', ' ', ' '), '123')
+  t.is(swapChar(null), '')
+  t.is(swapChar(undefined), '')
+  t.is(swapChar(), '')
+})