JavaScript Basics Cheat Sheet

Hello World:

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

Variables:

        
// Declaring variables
var age;
let pi;
const name = "John Smith";

// Assigning values
age = 25;
pi = 3.14159;

// Initializing variables
let count = 0;
const isTrue = true;
        
    

Data Types:

        
// Primitive data types
let number = 10;
let string = "Hello";
let boolean = true;
let nullValue = null;
let undefinedValue = undefined;

// Object data type
let object = {
    key1: value1,
    key2: value2
};

// Array data type
let array = [1, 2, 3, 4, 5];
        
    

Operators:

        
// Arithmetic operators
let sum = 5 + 3;
let difference = 10 - 4;
let division = 15 / 2;
let remainder = 15 % 2;
let product = 4 * 6;

// Comparison operators
let isEqual = (5 === 5);
let isGreater = (10 > 5);
let isLessThanOrEqual = (15 <= 20);

// Logical operators
let logicalAnd = true && false;
let logicalOr = true || false;
let logicalNot = !true;
        
    

Conditional Statements:

        
// If statement
if (condition) {
    // Code to execute if the condition is true
} else {
    // Code to execute if the condition is false
}

// Switch statement
let day = 3;
switch (day) {
    case 1:
        console.log("Monday");
        break;
    case 2:
        console.log("Tuesday");
        break;
    case 3:
        console.log("Wednesday");
        break;
    default:
        console.log("Invalid day");
        break;
}
        
    

Loops:

        
// While loop
while (condition) {
    // Code to execute while the condition is true
}

// For loop
for (initialization; condition; update) {
    // Code to execute repeatedly until the condition becomes false
}

// For...in loop
let object = {
    key1: value1,
    key2: value2
};
for (let key in object) {
    console.log(key + ": " + object[key]);
}

// For...of loop
let array = [1, 2, 3, 4, 5];
for (let element of array) {
    console.log(element);
}
        
    

Functions:

        
// Function declaration
function functionName(parameters) {
    // Code to execute
}

// Function expression
let multiply = function(a, b) {
    let result = a * b;
    return result;
};

// Arrow function
let divide = (a, b) => {
    let result = a / b;
    return result;
};

// Function call
functionName(arguments);
        
    

Objects:

        
// Object literal
let person = {
    name: "John",
    age: 25,
    greet: function() {
        console.log("Hello, my name is " + this.name);
    }
};

// Accessing object properties
let name = person.name;
person.age = 30;

// Calling object methods
person.greet();