Java Script

 Java Script Cheat Sheet

Here's a cheat sheet summarizing some of the common JavaScript concepts, functions, and syntax:

javascript

// JavaScript Cheat Sheet

// Variables
let variableName = value;     // Declare a variable with block scope
var variableName = value;     // Declare a variable with function scope (deprecated)
const constantName = value;   // Declare a constant variable

// Data Types
let number = 10;              // Number
let string = "Hello";         // String
let boolean = true;           // Boolean
let array = [1, 2, 3];        // Array
let object = {               // Object
    key1: value1,
    key2: value2
};

// Operators
let sum = num1 + num2;        // Addition
let difference = num1 - num2; // Subtraction
let product = num1 * num2;    // Multiplication
let quotient = num1 / num2;   // Division
let remainder = num1 % num2;  // Modulus
let isGreater = num1 > num2;  // Greater than
let isEqual = num1 === num2;  // Equality
let logicalAnd = condition1 && condition2;   // Logical AND
let logicalOr = condition1 || condition2;    // Logical OR
let logicalNot = !condition;                  // Logical NOT

// Conditionals
if (condition) {
    // Code executed if condition is true
}
else if (condition2) {
    // Code executed if condition2 is true
}
else {
    // Code executed if no previous conditions are true
}

// Loops
for (let i = 0; i < limit; i++) {
    // Code executed in each iteration
}

while (condition) {
    // Code executed repeatedly while condition is true
}

do {
    // Code executed at least once, then repeatedly while condition is true
} while (condition);

// Functions
function functionName(parameter1, parameter2) {
    // Code executed by the function
    return value;   // Optional return statement
}

// Arrays
let array = [1, 2, 3];        // Array declaration
let length = array.length;    // Length of the array
let element = array[index];   // Accessing an element
array.push(value);            // Add an element to the end
array.pop();                  // Remove the last element
array.unshift(value);         // Add an element to the beginning
array.shift();                // Remove the first element
array.splice(index, count);   // Remove or replace elements

// Objects
let object = {               // Object declaration
    key1: value1,
    key2: value2,
    method: function() {
        // Method code
    }
};
let value = object.key1;      // Accessing a value
object.key3 = value3;         // Adding a new key-value pair
delete object.key2;           // Deleting a key-value pair

// Events
element.addEventListener('event', function() {
    // Code executed when the event occurs
});

// DOM Manipulation
let element = document.getElementById('id');           // Get element by ID
let elements = document.getElementsByClassName('class');  // Get elements by class name
let elements = document.getElementsByTagName('tag');   // Get elements by tag name
element.innerHTML = 'Text';                              // Set element's HTML content
element.value = 'Value';                                  // Set element's value
element.style.property = 'value';                        // Set element's CSS style
element.classList.add('class');                           // Add a class to an element
element.classList.remove('class');                        // Remove a class from an element

// Promises (Asynchronous)
new Promise(function(resolve, reject) {
    // Asynchronous code
    if (success) {
        resolve(result);
    } else {
        reject(error);
    }
}).then(function(result) {
    // Code executed on successful promise
}).catch(function(error) {
    // Code executed on rejected promise
});

// Fetch API (HTTP Requests)
fetch(url)
    .then(function(response) {
        return response.json();
    })
    .then(function(data) {
        // Process the response data
    })
    .catch(function(error) {
        // Handle errors
    });

// Modules (ES6)
// Exporting module
export const variableName = value;
export function functionName() {
    // Code
}

// Importing module
import { variableName, functionName } from './module.js';

This cheat sheet covers some of the commonly used JavaScript concepts, functions, syntax, conditionals, loops, arrays, objects, events, DOM manipulation, promises, Fetch API, and modules. It serves as a handy reference for quick look-ups and reminders while working with JavaScript.