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JavaScript Cheatsheet

Array

Create Array


let myArray = ["Mr. White", "Mr. Orange", "Mr. Blonde", 
    "Mr. Pink", "Mr. Blue", "Mr. Brown"];

Loop


for (let name of myArray) {
    if (name === "Mr. Pink") {
        console.log("Encountered Mr. Pink. Breaking loop.");
        break; // Exit the loop when "Mr. Pink" is found
    }  
};

Add element


let newArray = [...myArray, "Nice Guy"];

Remove element


let newArray2 = myArray.filter(name => name !== "Nice Guy");

Check existence


newArray2.includes("Nice Guy");

List

Create a List


let myList = [1, 2, 3];

Remove


myList = myList.filter(item => item !== 2);

Loop


for (let item of myList) {
    console.log(item);
}

Check existence


myList.includes(3);

Get an element


let index = 1; // Index of element to get
let element = myList[index];

Dictionary

Create a dictionary


const myDictionary = {
    key1: 'value1',
    key2: 'value2',
};

Remove a key


delete myDictionary.key1;

Loop through keys and values


for (const key in myDictionary) {
    const value = myDictionary[key];
    console.log(key, value);
}

Check key existence


const keyExists = 'key2' in myDictionary;

Get a value by key


const value = myDictionary.key2;

Queue

Create a Queue


const queue = [];

Enqueue (Add) an Element


queue.push('element');

Dequeue (Remove) an Element


const removedElement = queue.shift();

Peek (Get First) Element


const firstElement = queue[0];

Check if Queue is Empty


const isEmpty = queue.length === 0;

Stack

Create a Stack


const stack = [];

Push (Add) an Element


stack.push('element');

Pop (Remove) an Element


const removedElement = stack.pop();

Peek (Get Top) Element


const topElement = stack[stack.length - 1];

Check if Stack is Empty


const isEmpty = stack.length === 0;