collectible_rarity_generator.js

function getRandomRarity(rarities) {
    // Convert rarities object to an array of [key, value] pairs
    const entries = Object.entries(rarities);

    // Sum of all probabilities
    const totalProbability = entries.reduce((sum, [, probability]) => sum + probability, 0);

    // Normalize the probabilities to ensure they sum up to 1
    if (totalProbability !== 1) {
        throw new Error("Total probability must sum up to 1");
    }

    // Generate a random number between 0 and 1
    const random = Math.random();

    let cumulativeProbability = 0;

    // Iterate over the entries to find the corresponding key
    for (const [key, probability] of entries) {
        cumulativeProbability += probability;
        if (random < cumulativeProbability) {
            return key;
        }
    }

    // Fallback in case of any floating-point arithmetic issues
    return entries[entries.length - 1][0];
}

// Example usage
const rarities = {
    rare: 0.1,
    legendary: 0.05,
    common: 0.5,
    uncommon: 0.35
};

const randomRarity = getRandomRarity(rarities);
console.log(randomRarity); // Output could be "common", "uncommon", "rare", or "legendary"