(BROKEN) A basic PRNG for client-side / web pages, which either resolves the RandomSource / Crypto object from the global Window, otherwise uses a sketchy, cryptographically insecure generator based on Math.random. Do not use this unless you don't need cryptographically secure randomness.

SMPRNG.js

// Sam's PRNG "proxy" for client-side JS, which generates random `UInt32`'s.
// Attempts to resolve the window's Crypto object and use its getRandomValues
// function if available, otherwise provides a cryptographically insecure PRN
// based on combining the current time and Math.random().
//
// Note: if any truthy argument is provided, the Fallback impl. will be used.
//       otherwise, attempts to use the Window's Crypto object if possible.
// Usage:
/// var prng = SMPRNG();
/// var uint = prng.next();
var SMPRNG = function(fallback) {
  
  // Returns a psuedo-random UInt32 generator. 
  // For use if a WindowRandomGenerator can not be constructed.
  FallbackRandomGen = (function() {
    _epoch = new Date().getTime();
    _min = 1;
    _max = Math.pow(2, 32);
    
    // XOR's the input value in an attempt to avoid duplicates from poor 
    // seed values using the current time in milliseconds from the UNIX epoch.
    _obfuscate = function(val) {
      _epoch += 1;
      return val ^ _epoch;
    };
    
    // Returns a value between the given min (inclusive) and max (exclusive) 
    // based on the provided value.
    _limitToRange = function(val, min, max) {
      min = Math.ceil(min);
      max = Math.floor(max);
      return Math.floor(val * (max - min) + min);
    };
    
    return {
      'next': function() {
        rand = _obfuscate(Math.random()) >>> 1;
        return _limitToRange(rand, _min, _max);
      }
    };
  });
  
  // If the fallback was requested
  if (fallback !== undefined && fallback != false) {
    return FallbackRandomGen();
  }
  
  // Constructs a random UInt32 generator based on a getRandomValues function.
  // SeeAlso: https://developer.mozilla.org/en-US/docs/Web/API/RandomSource
  WindowRandomGen = (function(getRandomValues) {
    source = {
      'getRandomValues': getRandomValues
    };
    return {
      'next': function() {
        array = new Uint32Array(1);
        source.getRandomValues(array);
        return array[0];
      }
    }
  });
  
  // Provide the Window's backing impl. if possible, otherwise the fallback.
  cryptoObj = (window.crypto || window.msCrypto) || {};
  getRandomValues = cryptoObj.getRandomValues;
  
  if (typeof(getRandomValues) === 'function') {
    return WindowRandomGen(getRandomValues);
  } else {
    return FallbackRandomGen();
  }
};