🧮 JavaScript Data Structures & Algorithms – The Foundation of Efficient Code

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🧲 Introduction – Why Learn Data Structures & Algorithms in JavaScript?

Whether you’re building complex applications or preparing for coding interviews, mastering data structures and algorithms (DSA) in JavaScript helps you write optimized, scalable, and readable code. JavaScript, being a flexible language, supports both procedural and functional paradigms—making it ideal for implementing DSA in both ways.

🎯 In this guide, you’ll learn:

• Common JavaScript data structures like lists, trees, and graphs
• Fundamental algorithms like sorting and recursion
• Functional programming techniques like higher-order functions and currying

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📘 Topics Covered

🔹 Topic	📄 Description
JavaScript Lists	Arrays and Linked Lists
JavaScript Trees	Binary Trees, Traversals
JavaScript Graphs	Representing and traversing graphs
JavaScript Sorting	Bubble, Quick, Merge Sort
JavaScript Recursion	Base case, stack trace, tail recursion
Functional Programming	Higher-order functions, pure functions
Currying & Composition	Code modularity and reusability

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📦 JavaScript — Data Structures

📌 JavaScript Lists

• Arrays are built-in list-like objects in JavaScript: let fruits = ["apple", "banana", "cherry"]; fruits.push("date"); // Add to end fruits.shift(); // Remove from start
• Linked Lists can be created manually using objects: class Node { constructor(data) { this.data = data; this.next = null; } }

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🌳 JavaScript Trees

• A tree is a hierarchical structure. The binary tree is most common: class TreeNode { constructor(value) { this.value = value; this.left = null; this.right = null; } }
• Tree traversal algorithms:
  • Inorder (Left → Root → Right)
  • Preorder (Root → Left → Right)
  • Postorder (Left → Right → Root)

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🌐 JavaScript Graphs

Graphs can be undirected or directed and are represented using:

• Adjacency list (using objects or Maps) const graph = { A: ["B", "C"], B: ["D"], C: [], D: ["A"] };
• DFS & BFS are key traversal algorithms.

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⚙️ JavaScript — Algorithms

🔁 JavaScript Sorting Algorithms

🔹 Bubble Sort

function bubbleSort(arr) {
  for (let i = 0; i < arr.length; i++)
    for (let j = 0; j < arr.length - i - 1; j++)
      if (arr[j] > arr[j + 1])
        [arr[j], arr[j + 1]] = [arr[j + 1], arr[j]];
  return arr;
}

🔹 Quick Sort (Divide & Conquer)

function quickSort(arr) {
  if (arr.length < 2) return arr;
  const pivot = arr[0];
  const left = arr.slice(1).filter(v => v <= pivot);
  const right = arr.slice(1).filter(v => v > pivot);
  return [...quickSort(left), pivot, ...quickSort(right)];
}

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🔁 JavaScript Recursion

Recursion is calling a function from itself.

function factorial(n) {
  if (n === 0) return 1;
  return n * factorial(n - 1);
}

✅ Use recursion when solving:

• Tree problems
• Graph traversal
• Backtracking

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🧠 JavaScript – Functional Programming Concepts

🔹 Higher-Order Functions (HOFs)

Functions that take other functions as arguments or return them.

const greet = () => console.log("Hi");
const executor = fn => fn();
executor(greet);

🔹 Pure Functions

• Same output for same input.
• No side effects.

🔹 Currying

Transforming a function with multiple arguments into a series of functions:

function multiply(a) {
  return function (b) {
    return a * b;
  };
}

const double = multiply(2);
console.log(double(5)); // 10

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📌 Summary – Recap & Next Steps

Data structures and algorithms are the core of efficient JavaScript programming. Whether you’re manipulating arrays, managing tree traversal, or applying functional techniques, these tools help improve both performance and readability.

🔍 Key Takeaways:

• JavaScript supports arrays, trees, and graphs natively or through OOP
• Sorting and recursion are foundational algorithms
• Functional programming enhances modularity and predictability

⚙️ Real-World Relevance:
Used in search engines, dynamic apps, form validation, dashboards, and interview problem-solving.

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❓ FAQs

Q1: Is JavaScript suitable for learning DSA?

✅ Yes, JavaScript supports both imperative and functional paradigms ideal for implementing DSA.

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Q2: When should I use recursion in JavaScript?

✅ Use recursion when problems can be broken into smaller similar subproblems—like traversing trees or graphs.

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Q3: What’s the difference between array and linked list?

✅ Arrays offer random access; linked lists are better for frequent insertions/deletions.

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Q4: Why use functional programming in JavaScript?

✅ It improves modularity, readability, and predictability of your code.

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Q5: Are JavaScript sorting methods optimized?

✅ Yes. Array.prototype.sort() uses an efficient, optimized algorithm (like Timsort in V8 engine).

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