Javascript Programming Language Cheatsheet

Cheatsheet for JavaScript covering some essential concepts. This cheatsheet covers some fundamental aspects of JavaScript.

Variables and Data Types

Declaration

let variableName;

Assignment

variableName = 10;

Data Types

let numberVar = 10;
let stringVar = "Hello";
let booleanVar = true;
let arrayVar = [1, 2, 3];
let objectVar = { key: 'value' };

Control Flow

Conditional Statements

if (condition) {
  // code to execute if condition is true
} else {
  // code to execute if condition is false
}

Loops

// Loops
for (let i = 0; i < 5; i++) {
  // code to repeat
}

while (condition) {
  // code to repeat as long as condition is true
}

Functions:

// Function Declaration
function functionName(parameter1, parameter2) {
  // code to execute
  return result;
}

// Function Expression
const add = function(a, b) {
  return a + b;
};

// Arrow Function
const multiply = (a, b) => a * b;

Arrays

let fruits = ['apple', 'orange', 'banana'];

// Accessing elements
let firstFruit = fruits[0];

// Adding elements
fruits.push('grape');

// Removing elements
let removedFruit = fruits.pop();

Objects

let person = {
  name: 'John',
  age: 30,
  isStudent: false
};

// Accessing properties
let personName = person.name;

// Modifying properties
person.age = 31;

DOM Manipulation

// Selecting elements
let element = document.getElementById('myElement');

// Modifying content
element.innerHTML = 'New content';

// Event handling
element.addEventListener('click', function() {
  // code to execute on click
});

Promises

// Creating a Promise
const myPromise = new Promise((resolve, reject) => {
  // code that may result in resolving or rejecting the promise
});

// Using a Promise
myPromise
  .then(result => {
    // code to execute when the promise is resolved
  })
  .catch(error => {
    // code to execute when the promise is rejected
  });

AJAX and Fetch

// Using Fetch API
fetch('https://api.example.com/data')
  .then(response => response.json())
  .then(data => {
    // code to handle the fetched data
  })
  .catch(error => {
    // code to handle errors
  });

Refer to the official documentation for more in-depth information and examples.

FAQ