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loianeloiane
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Merge pull request #236 from xingarr/add_features_array_chapter
feat: add array manipulation utilities for chunking, flattening, deduplication and rotation
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‎src/03-array/11-array-chunking.js‎

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// src/03-array/11-array-chunking.js
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/**
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* Array Chunking - Split an array into chunks of a specified size
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* Common use case: Pagination, batch processing, data visualization
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*/
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// Approach 1: Using slice method
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function chunkArray(array, chunkSize) {
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if (chunkSize <= 0) {
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throw new Error('Chunk size must be greater than 0');
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}
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const result = [];
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for (let i = 0; i < array.length; i += chunkSize) {
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result.push(array.slice(i, i + chunkSize));
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}
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return result;
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}
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// Approach 2: Using splice method (modifies original array)
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function chunkArraySplice(array, chunkSize) {
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if (chunkSize <= 0) {
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throw new Error('Chunk size must be greater than 0');
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}
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const result = [];
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const arrayCopy = [...array]; // Create a copy to avoid modifying original
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while (arrayCopy.length > 0) {
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result.push(arrayCopy.splice(0, chunkSize));
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}
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return result;
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}
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// Approach 3: Using reduce method (functional approach)
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function chunkArrayReduce(array, chunkSize) {
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if (chunkSize <= 0) {
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throw new Error('Chunk size must be greater than 0');
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}
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return array.reduce((chunks, item, index) => {
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const chunkIndex = Math.floor(index / chunkSize);
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if (!chunks[chunkIndex]) {
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chunks[chunkIndex] = []; // Start a new chunk
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}
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chunks[chunkIndex].push(item);
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return chunks;
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}, []);
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}
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// Examples
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console.log('=== Array Chunking Examples ===\n');
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const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
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console.log('Original array:', numbers);
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console.log('\nChunk size 3 (slice method):', chunkArray(numbers, 3));
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// Output: [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]]
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console.log('Chunk size 4 (splice method):', chunkArraySplice(numbers, 4));
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// Output: [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10]]
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console.log('Chunk size 2 (reduce method):', chunkArrayReduce(numbers, 2));
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// Output: [[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]]
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// Real-world example: Paginating data
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const users = [
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'Alice', 'Bob', 'Charlie', 'David', 'Eve',
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'Frank', 'Grace', 'Henry', 'Ivy', 'Jack'
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];
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const itemsPerPage = 3;
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const pages = chunkArray(users, itemsPerPage);
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console.log('\n=== Pagination Example ===');
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console.log(`Total users: ${users.length}`);
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console.log(`Items per page: ${itemsPerPage}`);
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console.log(`Total pages: ${pages.length}\n`);
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pages.forEach((page, index) => {
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console.log(`Page ${index + 1}:`, page);
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});
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// Edge cases
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console.log('\n=== Edge Cases ===');
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console.log('Empty array:', chunkArray([], 3));
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console.log('Chunk size larger than array:', chunkArray([1, 2], 5));
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console.log('Chunk size of 1:', chunkArray([1, 2, 3], 1));
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// to see the output of this file use the command: node src/03-array/11-array-chunking.js

‎src/03-array/11-array-chunking.ts‎

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// src/03-array/11-array-chunking.ts
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/**
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* Array Chunking - Split an array into chunks of a specified size
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* Common use case: Pagination, batch processing, data visualization
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*/
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// Approach 1: Using slice method
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function chunkArray<T>(array: T[], chunkSize: number): T[][] {
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if (chunkSize <= 0) {
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throw new Error('Chunk size must be greater than 0');
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}
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const result: T[][] = [];
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for (let i = 0; i < array.length; i += chunkSize) {
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result.push(array.slice(i, i + chunkSize));
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}
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return result;
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}
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// Approach 2: Using splice method (modifies original array)
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function chunkArraySplice<T>(array: T[], chunkSize: number): T[][] {
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if (chunkSize <= 0) {
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throw new Error('Chunk size must be greater than 0');
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}
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const result: T[][] = [];
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const arrayCopy = [...array]; // Create a copy to avoid modifying original
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while (arrayCopy.length > 0) {
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result.push(arrayCopy.splice(0, chunkSize));
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}
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return result;
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}
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// Approach 3: Using reduce method (functional approach)
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function chunkArrayReduce<T>(array: T[], chunkSize: number): T[][] {
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if (chunkSize <= 0) {
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throw new Error('Chunk size must be greater than 0');
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}
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return array.reduce((chunks: T[][], item: T, index: number) => {
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const chunkIndex = Math.floor(index / chunkSize);
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if (!chunks[chunkIndex]) {
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chunks[chunkIndex] = []; // Start a new chunk
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}
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chunks[chunkIndex].push(item);
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return chunks;
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}, []);
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}
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// Examples
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console.log('=== Array Chunking Examples ===\n');
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const numbers: number[] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
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console.log('Original array:', numbers);
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console.log('\nChunk size 3 (slice method):', chunkArray(numbers, 3));
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// Output: [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]]
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console.log('Chunk size 4 (splice method):', chunkArraySplice(numbers, 4));
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// Output: [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10]]
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console.log('Chunk size 2 (reduce method):', chunkArrayReduce(numbers, 2));
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// Output: [[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]]
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// Real-world example: Paginating data
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const users: string[] = [
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'Alice', 'Bob', 'Charlie', 'David', 'Eve',
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'Frank', 'Grace', 'Henry', 'Ivy', 'Jack'
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];
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const itemsPerPage = 3;
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const pages = chunkArray(users, itemsPerPage);
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console.log('\n=== Pagination Example ===');
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console.log(`Total users: ${users.length}`);
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console.log(`Items per page: ${itemsPerPage}`);
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console.log(`Total pages: ${pages.length}\n`);
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pages.forEach((page, index) => {
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console.log(`Page ${index + 1}:`, page);
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});
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// Edge cases
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console.log('\n=== Edge Cases ===');
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console.log('Empty array:', chunkArray([], 3));
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console.log('Chunk size larger than array:', chunkArray([1, 2], 5));
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console.log('Chunk size of 1:', chunkArray([1, 2, 3], 1));
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// to see the output of this file use the command: node src/03-array/11-array-chunking.ts

‎src/03-array/12-flatten-arrays.js‎

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// src/03-array/12-flatten-arrays.js
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/**
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* Flatten Nested Arrays - Convert multi-dimensional arrays into a single-dimensional array
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* Common use case: Data processing, tree traversal results, nested data structures
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*/
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// Approach 1: Using flat() method (ES2019+)
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function flattenSimple(array, depth = 1) {
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return array.flat(depth);
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}
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// Approach 2: Deep flatten using flat(Infinity)
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function flattenDeep(array) {
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return array.flat(Infinity);
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}
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// Approach 3: Recursive approach (custom implementation)
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function flattenRecursive(array) {
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const result = [];
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for (let item of array) {
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if (Array.isArray(item)) {
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result.push(...flattenRecursive(item));
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} else {
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result.push(item);
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}
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}
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return result;
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}
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// Approach 4: Using reduce (functional approach)
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function flattenReduce(array) {
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return array.reduce((acc, item) => {
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return acc.concat(Array.isArray(item) ? flattenReduce(item) : item);
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}, []);
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}
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// Approach 5: Iterative approach using stack
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function flattenIterative(array) {
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const stack = [...array];
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const result = [];
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while (stack.length) {
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const item = stack.pop();
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if (Array.isArray(item)) {
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stack.push(...item);
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} else {
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result.unshift(item); // Add to beginning since we're popping from end
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}
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}
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return result;
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}
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// Examples
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console.log('=== Flatten Arrays Examples ===\n');
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const nestedArray = [1, [2, 3], [4, [5, 6]], [[[7]]], 8];
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console.log('Original nested array:', JSON.stringify(nestedArray));
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console.log('\nFlat with depth 1:', flattenSimple(nestedArray, 1));
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// Output: [1, 2, 3, 4, [5, 6], [[7]], 8]
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console.log('Flat with depth 2:', flattenSimple(nestedArray, 2));
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// Output: [1, 2, 3, 4, 5, 6, [7], 8]
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console.log('Deep flatten (Infinity):', flattenDeep(nestedArray));
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// Output: [1, 2, 3, 4, 5, 6, 7, 8]
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console.log('Recursive flatten:', flattenRecursive(nestedArray));
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// Output: [1, 2, 3, 4, 5, 6, 7, 8]
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console.log('Reduce flatten:', flattenReduce(nestedArray));
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// Output: [1, 2, 3, 4, 5, 6, 7, 8]
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console.log('Iterative flatten:', flattenIterative(nestedArray));
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// Output: [1, 2, 3, 4, 5, 6, 7, 8]
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// Real-world example: Flattening category hierarchies
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console.log('\n=== Real-World Example: Category Hierarchy ===');
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const categories = [
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'Electronics',
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['Computers', ['Laptops', 'Desktops', ['Gaming PCs', 'Workstations']]],
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['Mobile', ['Smartphones', 'Tablets']],
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'Books',
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['Fiction', ['Sci-Fi', 'Fantasy']]
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];
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console.log('Original categories:', JSON.stringify(categories));
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console.log('Flattened categories:', flattenDeep(categories));
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// Performance comparison
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console.log('\n=== Performance Comparison ===');
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const largeNestedArray = [
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[1, 2, [3, 4]],
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[5, [6, [7, 8]]],
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[[9, 10], 11],
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[12, [13, [14, [15]]]]
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];
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console.time('flat(Infinity)');
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flattenDeep(largeNestedArray);
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console.timeEnd('flat(Infinity)');
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console.time('Recursive');
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flattenRecursive(largeNestedArray);
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console.timeEnd('Recursive');
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console.time('Reduce');
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flattenReduce(largeNestedArray);
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console.timeEnd('Reduce');
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console.time('Iterative');
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flattenIterative(largeNestedArray);
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console.timeEnd('Iterative');
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// Edge cases
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console.log('\n=== Edge Cases ===');
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console.log('Empty array:', flattenDeep([]));
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console.log('Already flat array:', flattenDeep([1, 2, 3, 4]));
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console.log('Array with empty arrays:', flattenDeep([1, [], [2, []], 3]));
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console.log('Mixed types:', flattenDeep([1, 'hello', [true, [null, undefined]], { key: 'value' }]));
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// to see the output of this file use the command: node src/03-array/12-flatten-arrays.js

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