How does Math.random() work in javascript?

by

Math.random() returns a Number value with a positive sign, greater than or equal to 0 but less than 1, chosen randomly or pseudo randomly with approximately uniform distribution over that range, using an implementation-dependent algorithm or strategy.

Here’s V8’s implementation:

uint32_t V8::Random() {

    // Random number generator using George Marsaglia's MWC algorithm.
    static uint32_t hi = 0;
    static uint32_t lo = 0;

    // Initialize seed using the system random(). If one of the seeds
    // should ever become zero again, or if random() returns zero, we
    // avoid getting stuck with zero bits in hi or lo by reinitializing
    // them on demand.
    if (hi == 0) hi = random();
    if (lo == 0) lo = random();

    // Mix the bits.
    hi = 36969 * (hi & 0xFFFF) + (hi >> 16);
    lo = 18273 * (lo & 0xFFFF) + (lo >> 16);
    return (hi << 16) + (lo & 0xFFFF);
}

Source: http://dl.packetstormsecurity.net/papers/general/Google_Chrome_3.0_Beta_Math.random_vulnerability.pdf

Here are a couple of related threads on StackOverflow:

More Related Contents:

  1. What exactly does Math.floor do?
  2. Slope function error(sort-of)… again [closed]
  3. What is JavaScript’s highest integer value that a number can go to without losing precision?
  4. Evaluating a string as a mathematical expression in JavaScript
  5. JavaScript % (modulo) gives a negative result for negative numbers
  6. How to find prime numbers between 0 – 100?
  7. Javascript: formatting a rounded number to N decimals
  8. How to transform black into any given color using only CSS filters
  9. Calculate date from week number in JavaScript
  10. Remove insignificant trailing zeros from a number?
  11. JavaScript exponents
  12. Is there a way to calculate 3D rotation on X and Y axis from a 4×4 matrix
  13. Read/Write bytes of float in JS
  14. Mixing two colors “naturally” in javascript
  15. Avoiding problems with JavaScript’s weird decimal calculations
  16. In JavaScript, why does zero divided by zero return NaN, but any other divided by zero return Infinity?
  17. How can I convert numbers into scientific notation?
  18. Convert 2:1 equirectangular panorama to cube map
  19. How can I round down a number in Javascript?
  20. JavaScript Number Split into individual digits
  21. Why is math.max() returning NaN on an array of integers?
  22. Javascript: Round up to the next multiple of 5
  23. Rounding numbers to 2 digits after comma
  24. Why does adding two decimals in Javascript produce a wrong result? [duplicate]
  25. JavaScript: Round to a number of decimal places, but strip extra zeros
  26. Display Good-looking Math Formula in Android
  27. Extracting the exponent and mantissa of a Javascript Number
  28. Javascript: PI (π) Calculator
  29. Javascript Math Error: Inexact Floats [duplicate]
  30. How to calculate with imaginary numbers in JavaScript?

Leave a Comment