The array is the most fundamental data structure in programming. Almost every complex structure — stacks, queues, heaps — is built on top of arrays internally.
📦 What is an Array?
An array stores elements in continuous memory locations, each accessible by an index starting at 0.
const fruits = ['Apple', 'Banana', 'Eggs', 'Juice'];
// fruits[0] = 'Apple', fruits[2] = 'Eggs'
If you want Eggs → directly go to index 2. No searching. That's the power of arrays.
⚡ How Arrays Work Internally
Arrays are stored in contiguous memory. This is why random access is O(1) — the computer calculates the address directly: base + (index × element_size).
🔑 Key Operations & Complexity
| Operation | Complexity | Why |
|---|---|---|
| Access arr[i] | O(1) | Direct memory jump |
| Search for value | O(n) | Must check each element |
| Insert at end | O(1) | Append to last slot |
| Insert at middle | O(n) | Must shift all elements right |
| Delete at middle | O(n) | Must shift all elements left |
💻 Common Array Operations in JavaScript
const arr = [10, 20, 30, 40];
console.log(arr[2]); // 30 — O(1)
arr.push(50); // O(1) — insert at end
arr.unshift(5); // O(n) — shifts everything
arr.pop(); // O(1) — delete last
arr.indexOf(30); // O(n) — linear scan
⚠️ When NOT to Use Arrays
- Frequent middle inserts/deletes → Use Linked List
- Key-value lookups → Use Hash Map
- LIFO operations → Use Stack
Part 3 of the Bitveen DSA Series. Originally published at bitveen.com