2.0.0

.gitignore

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+*.log
+.DS_Store
+node_modules
+dist

LICENSE

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+MIT License
+
+Copyright (c) 2020 Vien Dinh
+
+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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+# SuperMemo
+
+A JavaScript/TypeScript implementation of the [SuperMemo 2](https://super-memory.com/english/ol/sm2.htm) (SM2) algorithm for spaced based repetition flashcards.
+
+## Installation
+
+```
+npm install --save supermemo
+```
+
+## Usage
+
+```
+import { supermemo, SuperMemoItem } from 'supermemo';
+
+let item: SuperMemoItem = {
+  interval: 0,
+  repetition: 0,
+  efactor: 2.5,
+};
+
+console.log(item);
+
+item = supermemo(item, 5);
+console.log(item);
+
+item = supermemo(item, 4);
+console.log(item);
+```
+
+## References
+
+- [The SuperMemo 2 Algorithm explanation.](https://super-memory.com/english/ol/sm2.htm)
+- [The Delphi implementation of SuperMemo 2.](https://super-memory.com/english/ol/sm2source.htm)

package.json

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+{
+  "name": "supermemo",
+  "description": "A JavaScript/TypeScript implementation of the SuperMemo 2 (SM2) algorithm for spaced based repetition flashcards.",
+  "keywords": [
+    "sm2",
+    "supermemo",
+    "flashcard",
+    "supermemo-2",
+    "spaced-repetition"
+  ],
+  "author": "Vien Dinh",
+  "version": "2.0.0",
+  "license": "MIT",
+  "main": "dist/index.js",
+  "typings": "dist/index.d.ts",
+  "files": [
+    "dist"
+  ],
+  "scripts": {
+    "test": "tsdx test",
+    "build": "npx rimraf dist && tsc",
+    "prepare": "npm run build",
+    "lint": "tsdx lint"
+  },
+  "dependencies": {},
+  "devDependencies": {
+    "@types/jest": "^25.1.1",
+    "husky": "^4.2.1",
+    "tsdx": "^0.12.3",
+    "tslib": "^1.10.0",
+    "typescript": "^3.7.5"
+  },
+  "husky": {
+    "hooks": {
+      "pre-commit": "tsdx lint"
+    }
+  },
+  "prettier": {
+    "printWidth": 120,
+    "semi": true,
+    "singleQuote": true,
+    "trailingComma": "es5"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/Maxvien/supermemo.git"
+  },
+  "bugs": {
+    "url": "https://github.com/Maxvien/supermemo/issues"
+  },
+  "homepage": "https://github.com/Maxvien/supermemo#readme"
+}

src/index.ts

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+export * from './supermemo';

src/supermemo.test.ts

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+import { supermemo, SuperMemoItem } from './supermemo';
+
+describe('supermemo', () => {});

src/supermemo.ts

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+export interface SuperMemoItem {
+  interval: number;
+  repetition: number;
+  efactor: number;
+}
+
+export type SuperMemoGrade = 0 | 1 | 2 | 3 | 4 | 5;
+
+export function supermemo(item: SuperMemoItem, grade: SuperMemoGrade): SuperMemoItem {
+  let nextInterval: number;
+  let nextRepetition: number;
+  let nextEfactor: number;
+
+  if (grade >= 3) {
+    if (item.repetition === 0) {
+      nextInterval = 1;
+      nextRepetition = 1;
+    } else if (item.repetition === 1) {
+      nextInterval = 6;
+      nextRepetition = 2;
+    } else {
+      nextInterval = Math.round(item.interval * item.efactor);
+      nextRepetition = item.repetition + 1;
+    }
+  } else {
+    nextInterval = 1;
+    nextRepetition = 0;
+  }
+
+  nextEfactor = item.efactor + (0.1 - (5 - grade) * (0.08 + (5 - grade) * 0.02));
+
+  if (nextEfactor < 1.3) nextEfactor = 1.3;
+
+  return {
+    interval: nextInterval,
+    repetition: nextRepetition,
+    efactor: nextEfactor,
+  };
+}

tsconfig.json

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+{
+  "compilerOptions": {
+    "target": "es5",
+    "module": "CommonJS",
+    "lib": ["dom", "esnext"],
+    "importHelpers": true,
+    "declaration": true,
+    "sourceMap": false,
+    "strict": true,
+    "noImplicitAny": true,
+    "strictNullChecks": true,
+    "strictFunctionTypes": true,
+    "strictPropertyInitialization": true,
+    "noImplicitThis": true,
+    "alwaysStrict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "moduleResolution": "node",
+    "rootDir": "./src",
+    "outDir": "./dist",
+    "esModuleInterop": true
+  },
+  "include": ["src"],
+  "exclude": ["examples", "node_modules", "src/**/*.test.ts"]
+}