Random number generator.

rand.js

/**
 * Returns random numbers. See individual functions for docs.
 *
 * This function can be used as a shortcut function: by default, it will call
 * rand.int() using the arguments given to it. You can change which method it
 * will call by changing the rand.default string to any of the method names.
 */
function rand(length) {
  "use strict";

	if (this instanceof rand) {
		this.length = length;
	} else {
		return rand[rand.default].apply(this, arguments);
	}
}

// Default method to be called when calling rand().
rand.default = 'int';

(function (number, random, floor) {
	"use strict";

	/**
	 * Returns an object which the random methods can be called on to get an
	 * array of random numbers.
	 *
	 * rand.array(10).int(5, 10) will return an array of ten random numbers
	 * between 5 and 10.
	 *
	 * rand.array(7, 9).int(5, 10) will return an array of random length
	 * between 7 and 9 containing random numbers between 5 and 10.
	 *
	 * @param length Length. If maxlength specified, minimum length.
	 * @param maxlength Maximum length of the array.
	 * @returns rand object. Should only be used to call methods on.
	 */
	rand.array = function (length, maxlength) {
		if (typeof maxlength === 'number') {
			length = rand.int(length, maxlength);
		}

		return new rand(length);
	};

	/**
	 * Returns true or false.
	 * 
	 * @param prob Probability of returning true: default is 0.5.
	 * @returns {boolean}
	 */
	rand.bool = function (prob) {
		return random() < (prob || 0.5);
	};

	/**
	 * Returns a random float. If neither argument is specified, will return a
	 * random float between 0 and 1.
	 * 
	 * @param a If b is specified, lower range. Otherwise, upper range where
	 * lower range is 0.
	 * @param b Upper range.
	 * @returns {number} Random float.
	 */
	rand.float = function (a, b) {
		if (typeof a === number) {
			return typeof b === number ? random() * (b - a) + a : random() * a;
		} else {
			return random();
		}
	};

	/**
	 * Returns a random integer. In neither argument is specified, will return
	 * either 0 or 1.
	 * 
	 * @param a If b is specified, lower range. Otherwise, upper range where
	 * lower range is 0.
	 * @param b Upper range.
	 * @returns {number} Random integer.
	 */
	rand.int = function (a, b) {
		if (typeof a === number) {
			if (typeof b !== number) {
				b = a;
				a = 0;
			}
			return floor(rand.float(a, b + 1));
		} else {
			return floor(random() * 2);
		}
	};

	/**
	 * Internal function to return an array of length length containing random
	 * stuff.
	 * 
	 * @param length Length of returned array.
	 * @param func Function to be called to generate randomness.
	 * @param args Arguments to be given to the function.
	 * @returns {Array} Array of length length of randomness.
	 */
	var each = function (length, func, args) {
		for (var a = [], i = 0; i < length; i++) {
			a[i] = func.apply(this, args);
		}

		return a;
	};

	/**
	 * rand.array.bool() calls this: builds array and calls rand.bool().
	 * 
	 * @returns {Array} Array of rand.bool() calls.
	 */
	rand.prototype.bool = function () {
		return each(this.length, rand.bool, arguments);
	};
	
	/**
	 * rand.array.float() calls this: builds array and calls rand.float().
	 *
	 * @returns {Array} Array of rand.float() calls.
	 */
	rand.prototype.float = function () {
		return each(this.length, rand.float, arguments);
	};

	/**
	 * rand.array.int() calls this: builds array and calls rand.int().
	 *
	 * @returns {Array} Array of rand.int() calls.
	 */
	rand.prototype.int = function () {
		return each(this.length, rand.int, arguments);
	};
})('number', Math.random, Math.floor);