epam-short-track

Task 4. TS-Custom-lodash

Folder Name	Branch	Score	Coefficient
/ts-custom-lodash	ts-custom-lodash	300	0.7

Task Description

Your task is to implement ‘custom’ version of lodash library following next requirements:

1. Usage of methods from Array.prototype.* or Object.prototype.* is strictly forbidden.
2. You can create your own additional service functions (if needed).
3. You should use ES6+ features (any feature which supported by latest stable Chrome).
4. Lodash chain is out of scope
5. Please reuse as much of your code as possible

Requirements

• Create a folder named ts-custom-lodash.
• Install TypeScript, ESLint and Prettier as dev dependencies. You can use the following article Setting Up ESLint and Prettier for a TypeScript Project.
• Configure your project to use TypeScript, ESLint and Prettier.
• Add a TypeScript configuration file with (tsconfig.json):

  {
  "compilerOptions": {
    "rootDir": "./lib",
    "outDir": "./dist",
  
    "module": "system",
    "target": "es2015",
  
    "sourceMap": true,
    "declaration": true,
    "declarationMap": true,
  
    "noUncheckedIndexedAccess": true,
    "exactOptionalPropertyTypes": true,
  
    "strict": true,
    "noImplicitAny": true,
    "removeComments": true,
    "skipLibCheck": true
  }
  }
  

• Add a ESLint for TypeScript configuration file with the no-explicit-any rule enabled (eslint.config.mjs). There must be no ESLint errors. ```ts import tseslint from “@typescript-eslint/eslint-plugin”; import tsparser from “@typescript-eslint/parser”; import prettierPlugin from “eslint-plugin-prettier”; import prettierConfig from “eslint-config-prettier”;

export default [ { files: [“*/.ts”],

    languageOptions: {
        parser: tsparser,
        sourceType: "module",
    },

    plugins: {
        "@typescript-eslint": tseslint,
        prettier: prettierPlugin,
    },

    rules: {
        ...tseslint.configs.recommended.rules,
        ...prettierConfig.rules,
        "@typescript-eslint/no-unused-vars": "warn",
        "@typescript-eslint/no-explicit-any": "error",
        "no-console": "warn",
        semi: ["error", "always"],
        "no-warning-comments": [
            "warn",
            { terms: ["todo", "fixme", "xxx"], location: "anywhere" },
        ],
        "no-inline-comments": "warn",
        quotes: ["error", "double"],
        "prettier/prettier": "error",
    },
}, ]; ``` - Add a Prettier configuration file (`.prettierrc.json`). ```json {   "semi": true,   "singleQuote": false,   "tabWidth": 2,   "trailingComma": "all",   "printWidth": 100,   "arrowParens": "always" } ``` - Add scripts to `package.json`: ```json {   "name": "ts-custom-lodash",   "version": "1.0.0",   "main": "index.js",   "scripts": {
"lint": "npx eslint .",
"lint-fix": "npx eslint . --fix",
"prettier": "npx prettier --write ."   },   "keywords": [],   "author": "",   "license": "ISC",   "description": "",   "devDependencies": {
"@typescript-eslint/eslint-plugin": "^8.49.0",
"@typescript-eslint/parser": "^8.49.0",
"eslint": "^9.39.1",
"eslint-config-prettier": "^10.1.8",
"eslint-plugin-prettier": "^5.5.4",
"prettier": "^3.7.4",
"ts-node": "^10.9.2",
"typescript": "^5.9.3",
"typescript-eslint": "^8.49.0"   } } ``` ### Implementation Details

• Each function must be implemented in ts-custom-lodash/lib folder in a separate .ts file named after the function (e.g., chunk.ts, compact.ts, etc.).
• Create a utils folder for reusable helper functions.
• Add a types.ts or interfaces.ts file for shared types.
• The index.ts file in the ts-custom-lodash/lib folder must export all functions as follows:

  export { chunk } from './chunk';
  export { compact } from './compact';
  // ...etc for all functions
  

• Do not use the any type anywhere.
• Do not use any methods from Array.prototype.* or Object.prototype.*.
• Reuse your code as much as possible.
• Implement the following functions:

Implement for use cases where the arguments are Arrays:

• chunk
• compact
• drop
• dropWhile
• take
• filter
• find
• includes
• map
• zip

Implement for use cases where the arguments are Objects:

• merge
• omit
• omitBy
• pick
• pickBy
• toPairs

***Implement for all use cases from the docs:

• filter

---

Pull Request Requirements

Your Pull Request must include:

• Task URL.
• Submission Date / Deadline Date.
• Your self-check of the task’s completion using checkboxes.
• Any comments explaining your implementation decisions (if necessary).

---

Mentor Checklist

Maximum Score: 300 points

Criteria	Points
The branch is named ts-custom-lodash	5
Commit messages follow RS School Git Convention	5
The ts-custom-lodash folder exists	5
The ts-custom-lodash/lib folder exists	5
Each function is in its own .ts files	5
The ts-custom-lodash/lib/utils folder with reusable helper functions implemented	5
Add a ts-custom-lodash/lib/types.ts or ts-custom-lodash/lib/interfaces.ts file for shared types	5
The ts-custom-lodash/lib/index.ts file import and export all functions	5
The code uses Types or Interfaces	5
The code uses Everyday Types	5
The code uses Generics	5
The code uses Union Types	5
The code uses Object Types	5
The code uses Function Types	5
The code follows clean code principles and maximizes code reuse	10
ESLint is configured for TypeScript, no-explicit-any is enabled, and there are no errors	5
The TypeScript config includes "noImplicitAny": true and "strict": true	5
The .prettierrc.json file added	5
The package.json file includes scripts: “lint”, “lint-fix”, “prettier”	5
All dependencies added as dev dependencies	5
Implemented for use cases where the argument is an array.:
chunk	10
compact	10
drop	10
dropWhile	10
take	10
filter	10
find	10
includes	10
map	10
zip	10
Implemented for use cases where the arguments are Objects
merge	10
omit	10
omitBy	10
pick	10
pickBy	10
toPairs	10
Implement for all use cases from the docs
filter	20
Pull Request description includes all required elements:
Task URL is included in the PR	5
Submission and Deadline Dates are included in the PR	5
Your self-check of the task’s completion using checkboxes is included in the PR	5
Penalty:
Less than 3 commits in the PR	-20
Commit after the deadline and before mentor review	-20
The solution includes any comments	-50
The solution includes console.log	-10
Code is not fully covered with types	-50
ESLint errors	-10
Use of the any type	-300
Do not use any methods from Array.prototype.* or Object.prototype.*	-300

Notes

• Do not use any type anywhere.
• Do not use any methods from Array.prototype.* or Object.prototype.*.
• The solution must be well-structured, readable, and follow best practices.
• If any required element is missing or incorrect, points will be deducted accordingly.

This site is open source. Improve this page.