How to generate a random number in JavaScript
Łukasz Holeczek
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Generating random numbers is fundamental for creating games, sampling data, implementing randomized algorithms, and building features like random content selection or probabilistic behaviors in JavaScript applications.
With over 25 years of experience in software development and as the creator of CoreUI, I’ve implemented random number generation extensively in components like carousel shuffling, color generators, and interactive elements where unpredictable values enhance user engagement and functionality.
From my extensive expertise, the foundation for all random number generation is the built-in Math.random() function, which provides cryptographically weak but sufficient pseudo-random values.
This approach is simple, universally supported, and serves as the basis for more complex random number scenarios.
Use Math.random() to generate a random floating-point number between 0 (inclusive) and 1 (exclusive).
const randomFloat = Math.random()
// Result: e.g., 0.7834592847362841
const randomInRange = Math.random() * 10
// Result: e.g., 5.293847562847593 (0 to 10)
The Math.random() function returns a pseudo-random floating-point number greater than or equal to 0 and less than 1. In the first example, it might return something like 0.7834592847362841. To generate numbers in a specific range, multiply by the desired maximum: Math.random() * 10 produces numbers from 0 to 10 (exclusive). For a range between two values, use the formula Math.random() * (max - min) + min. For example, Math.random() * (50 - 10) + 10 generates numbers between 10 and 50.
Best Practice Note:
This is the same approach we use in CoreUI components for creating random colors, shuffling content, and implementing probabilistic UI behaviors across our component library.
For cryptographically secure random numbers, use crypto.getRandomValues() in browsers or crypto.randomBytes() in Node.js. The Math.random() function is deterministic and not suitable for security-sensitive applications. Always consider the range and precision requirements for your specific use case.
