Master JavaScript Stacks: Build, Use, and Apply Stack Operations

Stack

A stack is a Last‑In‑First‑Out (LIFO) linear data structure that allows operations only at one end, the top.

Because of its LIFO nature, elements not at the top cannot be accessed directly; to reach the bottom you must remove the elements above it.

Implementation in JavaScript

Define a Stack constructor that stores items in an internal array. function Stack(){ this.items = []; } Stack methods

push() – add an element to the top

pop() – remove and return the top element

size() – return the number of elements

empty() – return true if the stack is empty

peek() – return the top element without removing it

clear() – remove all elements

push

Insert a new element at the current top position.

function push(item){ this.items[this.top++] = item; }

pop

Remove and return the top element, decreasing the top index.

function pop(){ if(this.top===0) return; var item = this.items[--this.top]; this.items.length = this.top; return item; }

size function size(){ return this.top; } empty function empty(){ return this.top===0; } peek

function peek(){ return this.items[this.top-1]; }

clear

function clear(){ this.items = []; this.top = 0; }

Attach these methods to the Stack prototype:

Stack.prototype = { constructor: Stack, push: push, pop: pop, size: size, empty: empty, peek: peek, clear: clear };

Practical example

A recursive factorial function demonstrates stack usage.

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

Using a stack to compute factorial iteratively:

function factorial2(n){ var s = new Stack(), result = 1; while(n>1){ s.push(n--); } while(s.size()>0){ result *= s.pop(); } return result; }

Calling factorial2(5) yields 120.