Initial commit

.babelrc

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+{
+  "presets": [
+    [
+      "@babel/preset-env",
+      {
+        "targets": {
+          "node": "8"
+        }
+      }
+    ]
+  ]
+}

.editorconfig

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+# http://editorconfig.org
+root = true
+
+[*]
+end_of_line = lf
+charset = utf-8
+indent_size = 4
+indent_style = space
+trim_trailing_whitespace = true
+insert_final_newline = true

.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Typescript v1 declaration files
+typings/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# dotenv environment variables file
+.env
+
+# gatsby files
+.cache/
+public
+
+# Mac files
+.DS_Store
+
+# Yarn
+yarn-error.log
+.pnp/
+.pnp.js
+# Yarn Integrity file
+.yarn-integrity
+
+# Builds
+dist
+
+# Webpack
+.awcache

.nvmrc

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+12.14.1

.prettierrc

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+{
+  "printWidth": 100,
+  "singleQuote": true,
+  "useTabs": false,
+  "semi": true,
+  "tabWidth": 4,
+  "trailingComma": "none"
+}

.travis.yml

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+language: node_js
+
+cache:
+  yarn: true
+  directories:
+    - node_modules
+
+before_install:
+  - npm install -g yarn
+
+install:
+  - yarn --silent
+
+script:
+  - yarn run tscheck
+  - yarn run tslint
+  - yarn run test

LICENSE

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+MIT License
+
+Copyright (c) 2020 Luit Hollander
+
+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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+# Elfproef
+
+[![Travis CI](https://img.shields.io/travis/com/MrLuit/elfproef.svg?style=flat-square)](https://travis-ci.com/MrLuit/elfproef)
+[![Version](https://img.shields.io/npm/v/elfproef.svg?style=flat-square)](https://www.npmjs.com/package/elfproef)
+[![Dependencies](https://img.shields.io/david/MrLuit/elfproef.svg?style=flat-square)](https://david-dm.org/MrLuit/elfproef)
+[![License](https://img.shields.io/github/license/MrLuit/elfproef.svg?style=flat-square)](https://github.com/MrLuit/elfproef/blob/master/LICENSE)
+
+------
+
+Implementation of the 11-proof, a mathematical test used by the Dutch government for various digital identification numbers
+
+------
+
+## Description
+
+### Explanation
+Elfproef is Dutch for **11-proof** (`elf` means `11`, `proef` means `test`). It was originally designed to prevent people from trying to transfer money to a mistyped account number, specifically where either **one digit is incorrect**, or **2 digits were swapped**.
+
+The principle is very simple. First of all, a given number is split into its individual digits. Secondly, those digits are multiplied by their **"weight"**, a multiplier which is based on the position of the digit. Finally, the sum of all multiplied numbers is calculated. 
+
+If the result is **divisible by 11** and **greater than 0**, the 11-proof is _valid_.
+
+### Example
+A Dutch social security number (**BSN**) consists of 9 digits and must suffice the 11-proof with weights `[9, 8, 7, 6, 5, 4, 3, 2, -1]`.
+
+For a given BSN `ABCDEFGHI`, the outcome of the following formula must be divisble by 11 and greater than 0.
+
+```
+(9 × A) + (8 × B) + (7 × C) + (6 × D) + (5 × E) + (4 × F) + (3 × G) + (2 × H) + (-1 × I)
+```
+
+A valid BSN would be `111222333`. 
+```
+(9 × 1) + (8 × 1) + (7 × 1) + (6 × 2) + (5 × 2) + (4 × 2) + (3 × 3) + (2 × 3) + (-1 × 3) = 66
+```
+
+The result is greater than 0 and divisible by 11: 
+
+`66 > 0 66 ∧ 66 mod 11 = 0`
+
+## Usage
+
+### Installation
+`yarn add elfproef -E`
+
+### Example
+```
+import { validateBSN } from 'elfproef';
+
+const BSN = "111222333";
+const validBSN = validateBSN(BSN);
+
+console.log(validBSN);
+```
+
+## References
+- https://nl.wikipedia.org/wiki/Elfproef
+- https://nl.wikipedia.org/wiki/Burgerservicenummer
+- https://www.rijksoverheid.nl/onderwerpen/privacy-en-persoonsgegevens/vraag-en-antwoord/wat-is-het-burgerservicenummer-bsn
+
+## License
+
+This project is licensed under the [MIT License](https://github.com/MrLuit/elfproef/blob/master/LICENSE). 

package.json

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+{
+  "name": "elfproef",
+  "description": "Implementation of the 11-proof, a mathematical test used by the Dutch government for various digital identification numbers",
+  "version": "1.0.0",
+  "author": "Luit Hollander <[email protected]> (https://luit.me)",
+  "repository": "https://github.com/MrLuit/elfproef.git",
+  "license": "MIT",
+  "main": "./dist/elfproef.node.js",
+  "module": "./dist/elfproef.js",
+  "typings": "./typings/src/index.d.ts",
+  "keywords": [
+    "elfproef",
+    "11-proef",
+    "negenproef",
+    "9-proef",
+    "check digit",
+    "bsn"
+  ],
+  "scripts": {
+    "tscheck": "tsc --noEmit --project tsconfig.json",
+    "tslint": "tslint --project .",
+    "build": "cross-env NODE_ENV=production webpack --config ./webpack/config.ts",
+    "clean": "rimraf ./dist && rimraf ./typings",
+    "test": "mocha -r ts-node/register ./tests/**/*.ts",
+    "prettier:diff": "prettier --write --config ./.prettierrc --list-different \"src/**/*.ts\" \"tests/**/*.ts\" \"webpack/**/*.ts\""
+  },
+  "dependencies": {},
+  "devDependencies": {
+    "@babel/core": "7.8.3",
+    "@babel/preset-env": "7.8.3",
+    "@types/chai": "4.2.7",
+    "@types/mocha": "5.2.7",
+    "@types/node": "13.1.7",
+    "@types/webpack": "4.41.2",
+    "@types/webpack-merge": "4.1.5",
+    "@types/webpack-node-externals": "1.7.0",
+    "awesome-typescript-loader": "5.2.1",
+    "chai": "4.2.0",
+    "cross-env": "6.0.3",
+    "husky": "4.0.10",
+    "lint-staged": "9.5.0",
+    "mocha": "7.0.0",
+    "prettier": "1.19.1",
+    "rimraf": "3.0.0",
+    "ts-node": "8.6.2",
+    "tslint": "5.20.1",
+    "tslint-config-prettier": "1.18.0",
+    "tslint-microsoft-contrib": "6.2.0",
+    "typescript": "3.7.4",
+    "webpack": "4.41.5",
+    "webpack-cli": "3.3.10",
+    "webpack-merge": "4.2.2",
+    "webpack-node-externals": "1.7.2"
+  },
+  "lint-staged": {
+    "*.ts": [
+      "prettier --write --config ./.prettierrc --config-precedence file-override",
+      "tslint --project .",
+      "git add"
+    ]
+  },
+  "husky": {
+    "hooks": {
+      "post-commit": "git update-index --again",
+      "pre-commit": "lint-staged",
+      "pre-push": "npm run tslint && npm run tscheck && npm run test"
+    }
+  }
+}

src/index.ts

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+export const elfProef = (input: string | number, weights: number[]): boolean => {
+    if (typeof input === 'number') {
+        input = input.toString();
+    }
+    if (input.length !== weights.length) {
+        throw new Error('Amount of weights must be equal to length of input');
+    }
+    const numbers = input.split('');
+    const sum = numbers
+        .map((value: string, index: number) => {
+            const number = parseInt(value, 10);
+            const weight = weights[index];
+            return number * weight;
+        })
+        .reduce((a, b) => a + b);
+    return sum > 0 && sum % 11 === 0;
+};
+
+export const validateBSN = (input: string | number): boolean => {
+    if (typeof input === 'number') {
+        input = input.toString();
+    }
+    const validFormat = /^[\d]{9}$/.test(input);
+    if (validFormat) {
+        const validElfProef = elfProef(input, [9, 8, 7, 6, 5, 4, 3, 2, -1]);
+        return validElfProef;
+    } else {
+        return false;
+    }
+};

tests/index.ts

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+import { validateBSN } from '../src/index';
+import { expect } from 'chai';
+
+describe('BSN', () => {
+    it('string 111222333 should be valid', () => {
+        const result = validateBSN('111222333');
+        expect(result).to.be.true;
+    });
+    it('string 123456782 should be valid', () => {
+        const result = validateBSN('123456782');
+        expect(result).to.be.true;
+    });
+    it('string 000000000 should be invalid', () => {
+        const result = validateBSN('000000000');
+        expect(result).to.be.false;
+    });
+    it('string 999999999 should be invalid', () => {
+        const result = validateBSN('999999999');
+        expect(result).to.be.false;
+    });
+    it('number 111222333 should be valid', () => {
+        const result = validateBSN(111222333);
+        expect(result).to.be.true;
+    });
+    it('number 999999999 should be invalid', () => {
+        const result = validateBSN(999999999);
+        expect(result).to.be.false;
+    });
+});

tsconfig.json

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+{
+  "compilerOptions": {
+    "baseUrl": "./src/",
+    "sourceMap": true,
+    "strictNullChecks": true,
+    "allowSyntheticDefaultImports": true,
+    "module": "commonjs",
+    "lib": ["dom", "es2017"],
+    "declaration": true,
+    "declarationDir": "typings",
+    "outDir": "./dist",
+    "target": "es2017",
+    "noEmitOnError": true,
+    "strict": true,
+    "experimentalDecorators": true,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "resolveJsonModule": true
+  },
+  "include": [
+    "./src/**/*",
+    "./tests/**/*",
+    "./webpack/**/*",
+  ],
+  "exclude": [
+    "node_modules"
+  ]
+}