Random Numbers in JavaScript

Our random number generation example demonstrates how to generate pseudorandom numbers in JavaScript.

// In JavaScript, we use the Math.random() function to generate random numbers

function main() {
    // Math.random() returns a float between 0 (inclusive) and 1 (exclusive)
    // To get an integer between 0 and 99:
    console.log(Math.floor(Math.random() * 100) + "," + 
                Math.floor(Math.random() * 100));

    // Math.random() directly gives a float between 0 and 1
    console.log(Math.random());

    // To get a float between 5 and 10:
    console.log((Math.random() * 5 + 5) + "," +
                (Math.random() * 5 + 5));

    // For reproducible random numbers, we can use a seeded random number generator
    // Here's a simple implementation of a seeded random number generator
    function seededRandom(seed) {
        let x = Math.sin(seed++) * 10000;
        return x - Math.floor(x);
    }

    let seed = 42;
    console.log(Math.floor(seededRandom(seed) * 100) + "," +
                Math.floor(seededRandom(seed + 1) * 100));

    // Using the same seed will produce the same sequence
    seed = 42;
    console.log(Math.floor(seededRandom(seed) * 100) + "," +
                Math.floor(seededRandom(seed + 1) * 100));
}

main();

You can run this script using Node.js:

$ node random-numbers.js
68,56
0.8090228139659177
5.840125017402497,6.937056298890035
94,49
94,49

Note that the built-in Math.random() in JavaScript doesn’t support seeding. For more advanced random number generation with seeding capabilities, you might want to use a library like seedrandom.

JavaScript’s Math object provides other methods for random number operations, such as Math.round(), Math.ceil(), and Math.floor() which can be useful when working with random numbers.

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Random Numbers in JavaScript