index.js

"use strict";

/**
 * Provides a suite of functions for generating random data.
 * @class Random
 * @constructor
 * @static
 */
var random = module.exports;

/**
 * Quick reference array for generating random strings
 * @private
 * @property alphanumeric
 * @type String[]
 */
var alphanumeric = ["0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];

/**
 * Quick reference array for generating random strings with lowercase only.
 * @private
 * @property alphanumericLower
 * @type String[]
 */
var alphanumericLower = ["0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];

/**
 * 
 * @type Number[]
 * @property primes
 * @private
 */
var primes = [
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/**
 * Method for getting a random floating point number x | min <= x < min + range
 * As an example, random(5) will yield a number between 0 and 5 where as
 * random(5,5) will yield a number between 5 and 10.
 * @method number
 * @param {Number} range The "width" of the range of numbers desired.
 * @param {Number} min The minimum number desired.
 * @return {Number} A random number.
 */
random.number = function(range, min) {
	if(min) {
		return Math.random() * range + min;
	}
	return Math.random() * range;
};

/**
 * Method for getting a random integer x | min <= x < min + range
 * As an example, random(5) will yield a number between 0 and 4 where as
 * random(5,5) will yield a number between 5 and 9.
 * @method integer
 * @param {Number} range The "width" of the range of numbers desired.
 * @param {Number} min The minimum number desired.
 * @return {Number} A random number.
 */
random.integer = function(range, min) {
	if(min) {
		return Math.floor(Math.random() * range + min);
	}
	return Math.floor(Math.random() * range);
};

/**
 * Get a random alphanumeric string (ie. matches pattern ^[a-zA-Z0-9]*$).
 * @method string
 * @param {Number} len The desired length for the returned String.
 * @return {String} A random alphanumeric string
 */
random.string = function(len) {
	if(len) {
		var x, string = [];
		for(x=0; x<len; x++)
			string[x] = alphanumeric[random.integer(alphanumeric.length)];
		return string.join("");
	} else {
		return null;
	}
};

/**
 * Get a random alphanumeric string (ie. matches pattern ^[a-zA-Z0-9]*$).
 * @method string
 * @param {Number} len The desired length for the returned String.
 * @return {String} A random alphanumeric string
 */
random.lowercase = function(len) {
	if(len) {
		var x, string = [];
		for(x=0; x<len; x++)
			string[x] = alphanumericLower[random.integer(alphanumericLower.length)];
		return string.join("");
	} else {
		return null;
	}
};

/**
 * Get a normal distribution of random numbers between 2 values.
 * @see https://stackoverflow.com/questions/25582882/javascript-math-random-normal-distribution-gaussian-bell-curve
 * @method guassian
 * @param {Number} [mean] Optional, defaults to 0.
 * @param {Number} [stdev] Optional, detaults to 1.
 * @param {Number} [skew] Optional skew of the curve, defaults to 1. Higher numbers front load the curve, fractions back load the curve.
 * 		Negative numbers are not valid here.
 */
random.guassian = function(min = 0, max = 1, skew = 1) {
	if(skew <= 0) {
		return 0;
	}

	var num = Math.sqrt(-2 * Math.log(1 - Math.random())) * Math.cos(2 * Math.PI * Math.random());
	return Math.pow(num/10 + .5, skew) * (max - min) + min;
};

/**
 * Returns a prime number from a pre-generated list.
 * 
 * This should not be considered for security generation purposes.
 * @method prime
 * @return {Number} A random prime number.
 */
random.prime = function() {
	return primes[random.integer(primes.length)];
};

/**
 * Create a unique identifier following a pattern;
 * [prefix] : [string.length = pre] [Timestamp] [length? string.len = remaining]
 * 
 * Example:  
 * Random.identified('example', 2, 3)  
 *  > "example:Ha1527351401496iUo"
 * 
 * @method identified
 * @param {String} prefix The string to prefix the identifier with before the colon (':').
 * 		Defaults to 'id'.
 * @param {Number} pre Length of the randomly generate string before the timestamp.
 * 		Defaults to 10.
 * @param {Number} length The total desired length of the randomized section of the identifier.
 * 		Fills in after the time stamp if additional length is needed. 
 * 
 */
random.identifier = function(prefix, pre, length) {
	if(prefix === undefined) {
		prefix = "id";
	}
	if(pre === undefined) {
		pre = 10;
	}
	
	var id = random.string(pre) + Date.now();
	if(length) {
		id += random.string(length - id.length);
	}
	
	return prefix + ":" + id;
};