Stack

What it is

A stack is a LIFO structure:

last in, first out.

The most recent item is the first one to come back out.

In JavaScript

The simplest version uses an array with push and pop:

const stack: string[] = []

stack.push('(')
stack.pop()

When to use it

It usually fits when the problem asks you to:

• undo the most recent step
• close something that was opened before
• keep temporary context

Better question

Instead of memorizing the name, ask:

1. does the most recently opened item need to be handled first?
2. is there a natural undo order here?
3. do I need short, reversible history?