JavaScript Random Numbers

Common Random Patterns

// 1 to 10
Math.floor(Math.random() * 10) + 1;

// Random hex color
"#" + Math.floor(Math.random()*16777215).toString(16);

let arr = ["apple", "banana", "orange"];
arr[Math.floor(Math.random() * arr.length)];

// 50/50 chance
Math.random() < 0.5;

🔹 Random Integers

Generate random whole numbers in different ranges:

// Random integer from 0 to 9
let random0to9 = Math.floor(Math.random() * 10);
console.log("0-9:", random0to9);

// Random integer from 1 to 10
let random1to10 = Math.floor(Math.random() * 10) + 1;
console.log("1-10:", random1to10);

// Random integer from 5 to 15
let random5to15 = Math.floor(Math.random() * 11) + 5;
console.log("5-15:", random5to15);

// Generic function for any range
function randomInt(min, max) {
    return Math.floor(Math.random() * (max - min + 1)) + min;
}

console.log("Random 20-30:", randomInt(20, 30));
console.log("Random 100-200:", randomInt(100, 200));

// Test the function multiple times
for (let i = 0; i < 5; i++) {
    console.log("Dice roll:", randomInt(1, 6));
}

🔹 Random Decimals

Generate random decimal numbers in specific ranges:

// Random decimal from 0 to 1 (default)
console.log("0-1:", Math.random());

// Random decimal from 0 to 100
let random0to100 = Math.random() * 100;
console.log("0-100:", random0to100);

// Random decimal from 10 to 20
let random10to20 = Math.random() * 10 + 10;
console.log("10-20:", random10to20);

// Generic function for decimal range
function randomFloat(min, max, decimals = 2) {
    let num = Math.random() * (max - min) + min;
    return Math.round(num * Math.pow(10, decimals)) / Math.pow(10, decimals);
}

console.log("Random 1.5-5.5:", randomFloat(1.5, 5.5));
console.log("Random price $10-$50:", "$" + randomFloat(10, 50, 2));

// Random percentage
function randomPercentage() {
    return randomFloat(0, 100, 1) + "%";
}

console.log("Random percentage:", randomPercentage());

🔹 Random Array Elements

Pick random items from arrays:

// Random array element
let fruits = ["apple", "banana", "orange", "grape", "kiwi"];
let randomFruit = fruits[Math.floor(Math.random() * fruits.length)];
console.log("Random fruit:", randomFruit);

// Generic function
function randomChoice(array) {
    return array[Math.floor(Math.random() * array.length)];
}

let colors = ["red", "blue", "green", "yellow", "purple"];
console.log("Random color:", randomChoice(colors));

// Multiple random choices (with possible repeats)
function randomChoices(array, count) {
    let choices = [];
    for (let i = 0; i < count; i++) {
        choices.push(randomChoice(array));
    }
    return choices;
}

console.log("3 random fruits:", randomChoices(fruits, 3));

// Random choice without repeats
function randomUniqueChoices(array, count) {
    let shuffled = [...array].sort(() => 0.5 - Math.random());
    return shuffled.slice(0, count);
}

console.log("3 unique fruits:", randomUniqueChoices(fruits, 3));

🔹 Random Booleans and Probability

Create random true/false values and probability-based outcomes:

// Simple 50/50 random boolean
let coinFlip = Math.random() < 0.5;
console.log("Coin flip:", coinFlip ? "Heads" : "Tails");

// Custom probability (30% chance of true)
let thirtyPercent = Math.random() < 0.3;
console.log("30% chance:", thirtyPercent);

// Probability function
function randomChance(percentage) {
    return Math.random() < (percentage / 100);
}

console.log("75% chance:", randomChance(75));
console.log("10% chance:", randomChance(10));

// Weighted random choice
function weightedChoice(choices, weights) {
    let totalWeight = weights.reduce((sum, weight) => sum + weight, 0);
    let random = Math.random() * totalWeight;
    
    for (let i = 0; i < choices.length; i++) {
        random -= weights[i];
        if (random <= 0) {
            return choices[i];
        }
    }
}

let outcomes = ["common", "uncommon", "rare", "legendary"];
let probabilities = [50, 30, 15, 5]; // percentages

console.log("Loot drop:", weightedChoice(outcomes, probabilities));

🔹 Practical Random Examples

Real-world applications of random numbers:

// Random password generator
function generatePassword(length = 8) {
    let chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    let password = "";
    for (let i = 0; i < length; i++) {
        password += chars[Math.floor(Math.random() * chars.length)];
    }
    return password;
}

console.log("Random password:", generatePassword(10));

// Random hex color
function randomHexColor() {
    return "#" + Math.floor(Math.random() * 16777215).toString(16).padStart(6, '0');
}

console.log("Random color:", randomHexColor());

// Shuffle array (Fisher-Yates algorithm)
function shuffleArray(array) {
    let shuffled = [...array];
    for (let i = shuffled.length - 1; i > 0; i--) {
        let j = Math.floor(Math.random() * (i + 1));
        [shuffled[i], shuffled[j]] = [shuffled[j], shuffled[i]];
    }
    return shuffled;
}

let deck = ["A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"];
console.log("Shuffled deck:", shuffleArray(deck));

// Random quote generator
let quotes = [
    "The only way to do great work is to love what you do.",
    "Innovation distinguishes between a leader and a follower.",
    "Stay hungry, stay foolish.",
    "Your time is limited, don't waste it living someone else's life."
];

function randomQuote() {
    return randomChoice(quotes);
}

console.log("Random quote:", randomQuote());