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Last In First Out (LIFO) data structure
| Operations | Complexity |
|---|---|
| Push (insert end) | O(1) |
| Pop (delete last) | O(1) |
| Peek (view last) | O(1) |
class Stack {
constructor() {
this.items = [];
}
push(element) {
this.items.push(element);
}
pop() {
if (this.items.length == 0) {
throw new Error('stack is empty');
}
return this.items.pop();
}
peek() {
return this.items.at(-1);
}
}
const myStack = new Stack();
myStack.push('One');
myStack.push('Two');
myStack.push('Three');
console.log(myStack.peek()); // Three
console.log(myStack.pop()); // Three
console.log(myStack.pop()); // Two
console.log(myStack.pop()); // One
console.log(myStack.peek()); // undefined
class StackNode {
constructor(value) {
this.value = value;
this.next = null;
}
}
class Stack {
constructor() {
this.top = null;
this.size = 0;
}
push(value) {
const newNode = new StackNode(value);
newNode.next = this.top;
this.top = newNode;
this.size++;
}
pop() {
if (this.top === null) {
throw new Error('stack is empty');
}
const value = this.top.value;
this.top = this.top.next;
this.size--;
return value;
}
peek() {
if (this.top === null) {
throw new Error('stack is empty');
}
return this.top.value;
}
}
const myStack = new Stack();
myStack.push('One');
myStack.push('Two');
myStack.push('Three');
console.log(myStack.peek()); // Three
console.log(myStack.pop()); // Three
console.log(myStack.pop()); // Two
console.log(myStack.pop()); // One
console.log(myStack.peek()); // Error: stack is empty