JavaScript Cheat Sheets

console.log("Hello, World!");

let num = Number("123"); // 123
let str = String(123); // "123"

let x = 10;
if (x > 5) {
    console.log("Greater");
} else {
    console.log("Smaller or equal");
}

let day = 2;
switch (day) {
    case 1:
        console.log("Monday");
        break;
    case 2:
        console.log("Tuesday");
        break;
    default:
        console.log("Other");
}

for (let i = 0; i < 5; i++) {
    console.log(i);
}

let arr = [1,2,3];
for (let n of arr) {
    console.log(n);
}

let i = 0;
while (i < 3) {
    console.log(i);
    i++;
}

let i = 0;
do {
    console.log(i);
    i++;
} while (i < 3);

function greet(name) {
    return "Hello, " + name;
}

const greet = (name) => "Hello, " + name;

function makeCounter() {
    let count = 0;
    return function() {
        return count++;
    };
}

let car = {
    brand: "Toyota",
    start: function() {
        console.log(this.brand + " is starting");
    }
};

let arr = [1, 2, 3];
arr.push(4); // [1, 2, 3, 4]
arr.pop(); // [1, 2, 3]

function Person(name) {
    this.name = name;
}
Person.prototype.greet = function() {
    console.log("Hello, " + this.name);
};

let x = 10;
const y = 20;

let name = "World";
console.log(`Hello, ${name}!`);

let [a, b] = [1, 2];
let {name, age} = {name: "Alice", age: 25};

function fetchData(callback) {
    setTimeout(() => {
        callback("Data fetched");
    }, 1000);
}

let promise = new Promise((resolve, reject) => {
    resolve("Success");
});
promise.then(result => console.log(result));

async function fetchData() {
    let data = await fetch("/api/data");
    console.log(data);
}

let element = document.querySelector("#myElement");

element.addEventListener("click", function() {
    console.log("Element clicked");
});

try {
    let x = 1 / 0;
} catch (e) {
    console.log("Error: " + e.message);
}

class MyError extends Error {
    constructor(message) {
        super(message);
        this.name = "MyError";
    }
}

function map(arr, func) {
    let result = [];
    for (let i = 0; i < arr.length; i++) {
        result.push(func(arr[i]));
    }
    return result;
}

(function() {
    console.log("IIFE");
})();

export function greet() {
    console.log("Hello");
}
import { greet } from "./module.js";

console.log("Start");
setTimeout(() => {
    console.log("Timeout");
}, 0);
console.log("End");

let regex = /\d+/;
console.log(regex.test("123"));

console.log("Debugging");
debugger;

fetch("/api/data")
    .then(response => response.json())
    .then(data => console.log(data));

let socket = new WebSocket("ws://example.com/socket");
socket.onmessage = function(event) {
    console.log("Data received: " + event.data);
};

let message: string = "Hello, TypeScript!";

test("adds 1 + 2 to equal 3", () => {
    expect(1 + 2).toBe(3);
});