74 lines
2.1 KiB
Markdown
74 lines
2.1 KiB
Markdown
---
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title: JavaScript Data Structures - Stack
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shortTitle: Stack
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type: story
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tags: javascript,object,class,array
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author: chalarangelo
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cover: blog_images/purple-flower-macro-1.jpg
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excerpt: A stack is a linear data structure which follows a last in, first out (LIFO) order of operations.
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firstSeen: 2021-08-03T05:00:00-04:00
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---
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### Definition
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A stack is a linear data structure that behaves like a real-world stack of items. It follows a last in, first out (LIFO) order of operations, similar to its real-world counterpart. This means that new items are added to the top of the stack and items are removed from the top of the stack as well.
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The main operations of a stack data structure are:
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- `push`: Adds an element to the top of the stack
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- `pop`: Removes an element from the top of the stack
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- `peek`: Retrieves the element at the top of the stack, without removing it
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- `isEmpty`: Checks if the stack is empty
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### Implementation
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```js
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class Stack {
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constructor() {
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this.items = [];
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}
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push(item) {
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this.items.unshift(item);
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}
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pop(item) {
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return this.items.shift();
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}
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peek(item) {
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return this.items[0];
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}
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isEmpty() {
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return this.items.length === 0;
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}
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}
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```
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- Create a `class` with a `constructor` that initializes an empty array, `items`, for each instance.
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- Define a `push()` method, which uses `Array.prototype.unshift()` to add an element to the start of the `items` array.
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- Define a `pop()` method, which uses `Array.prototype.shift()` to remove an element from the start of the `items` array.
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- Define a `peek()` method, which retrieves the value of the first element in the `items` array, without removing it.
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- Define an `isEmpty()` method, which uses `Array.prototype.length` to determine if the `items` array is empty.
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```js
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const stack = new Stack();
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stack.push('apples');
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stack.push('oranges');
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stack.push('pears');
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stack.isEmpty(); // false
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stack.peek(); // 'pears'
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stack.pop(); // 'pears'
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stack.pop(); // 'oranges'
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stack.pop(); // 'apples'
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stack.isEmpty(); // true
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```
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