I have a simple vat calculator, but there is something funny with one of the calculation. The problem is in the last column, saying moms. e=a + d * 0.25 is correct, but the code below is not. It shows a too big number when calculating.
JS Code:
$(document).ready(function() {
$('#submit').click(function() {
//get cost and check value
var cost = $('#cost').val();
var check = $('#checkBox');
if (cost != null && cost != "") {
if (cost < 350) {
//c = a * 1
$('#total').val(cost);
$('#toll').val("");
$('#moms').val("");
} else {
if (check.is(':checked')) {
//c = a* 1.107* 1.25
$('#total').val((cost * 1.107 * 1.25).toFixed(2));
//d = a * 0.107
$('#toll').val((cost * 0.107).toFixed(2));
} else {
$('#total').val((cost * 1.25).toFixed(2));
$('#toll').val("");
$('#moms').val("");
}
if ($('#toll').val() != null && $('#toll').val() != "") {
//e = (a + d) * 0.25
var moms = (cost + $('#toll').val()) * 0.25;
$('#moms').val(moms.toFixed(2));
}
}
}
})
});
The value of input elements will always be a string. In most of your code, you're using the "cost" value in such a way that it will be implicitly converted to a number. However, the + operator is different, and will preferentially perform string concatenation to addition.
If you explicitly force the cost to be a number when you initialize it, things should work better:
var cost = +$('#cost').val();
That leading unary + operator will force the string value to be treated as a number. Now, of course, if the string doesn't look like a good number, then cost will be set to NaN, so you should check for that:
if (!isNaN(cost)) {
That can replace your current check to see if cost is not empty.
edit Sorry, you'll also need to convert the value of $('#toll').val() so that line would look like:
var moms = (cost + +$('#toll').val()) * 0.25;
The JavaScript + operator really likes strings.
I'm trying to generate two numbers with a specific sum. Here is my proposed method:
Edited: http://jsfiddle.net/KDmwn/274/
$(document).ready(function () {
function GenerateRandomNumber() {
var min = -13, max = 13;
var random = Math.floor(Math.random() * (max - min + 1)) + min;
return random;
}
var x = GenerateRandomNumber();
function GenerateRandomNumber2() {
var min2 = -13, max2 = 13;
var random2 = Math.floor(Math.random() * (max2 - min2 + 1)) + min2;
if ((random2 + x) == 0){
return random2};
}
var xx = GenerateRandomNumber2();
There's something wrong with the if ((random2 + x) = 0) line, as the code runs perfectly fine when it's removed. How can I modify this line so that the sum of the two numbers is 0? It would be most helpful if someone could modify the Jsfiddle that I've included. Thanks!
This is invalid:
if ((random2 + x) = 0){
You cannot assign something to an expression.
You probably meant to use the comparison operator (==), like this:
if ((random2 + x) == 0){
Are you trying to make it only output a second number that, when added to the first, equals 0? Because it actually already does that - but only if it gets it on the first try (try hitting refresh at least 30 times.) You need to tell it to keep re-choosing (looping) the second random number while the sum isn't 0:
function GenerateRandomNumber2() {
var min2 = -13,
max2 = 13;
var random2;
while ((random2 + x) !== 0) {
random2 = Math.floor(Math.random() * (max2 - min2 + 1)) + min2;
}
return random2;
}
http://jsfiddle.net/vL77hjp0/
To take this one step further, if I'm reading this right (if not ignore this) it looks like you might want to eventually choose a random sum and have it determine the required second number to be added. To do this, we would replace the 0 in our "while" loop with 'sum'. And 'sum' would have to be defined as a random number with a "max=x+13" and "min=x-13" (otherwise the random number may be too high/low for random2 to ever reach, causing the browser to crash.) [Or just remove the limits from random2.]
http://jsfiddle.net/fkuo54hc/
First, your GenerateRandomNumbers2 function returns undefined value other than in your if statement. So you need to return a value. I updated your fiddle and refactor some of your code.
I want to add a random modifier to this code, something that will either add to or subtract from the damage based off of a range of +-20% of the base value. The damage would randomize between a range of 80% of result to 120% of result. For a numeric example:
attacker.Strength(20) - defender.Defense(10) = result
20 - 10 = range(8 to 12)
var Fight = function (attacker, defender) {
var result;
result = (attacker.Strength - defender.Defense);
defender.HP = defender.HP - result;
if(defender.HP >= 1) {
return defender.Name + " has taken " + result + " damage!";
} else {
return defender.Name + " has been slain";
}
};
Math.random returns a number between zero and one. Map this to your range from 0.8 to 1.2 with this:
var factor = Math.random() * 0.4 + 0.8;
// | | |
// [0, 1[ | |
// \ / |
// [0, 0.4[ /
// \ /
// [0.8, 1,2[
var result = Math.round((attacker.Strength - defender.Defense) * factor);
Not sure whether you want to round somewhere so that your player's health points are always natural numbers. If not, you should change your death condition to defender.HP > 0.
As in Math.random() * 0.4?
result = (attacker.Strength - defender.Defense) * (0.8 + Math.random() * 0.4);
For eaxact +/- 20%, use random to generate two numbers only i.e. 0, 1.
If 0, treat it as + and if 1, treat it as - e.g. below:
var randomNum = Math.round(Math.random()); //it will return 0 or 1
if(randomNum ==0){
//write +20% code here
result = (attacker.Strength - defender.Defense)*1.2;
}else{
//write -20% code here
result = (attacker.Strength - defender.Defense)*0.8;
}
EDIT: For range based, its much simpler.
var factor = 0.8 + Math.random()*0.4;
result = (attacker.Strength - defender.Defense)*factor ;
As the title says ... is it possible to create a random 16 digit number with jquery?
Just use:
Math.floor(Math.random()*1E16)
EDIT :
Note that there is about a 1/10 chance of a lower number of digits. If Math.random() generates something like 0.0942104924071337 then 0.0942104924071337 * 1E16 is 0942104924071337 which evaluates to 942104924071337; a 15 digit number.
The only way to 100% guarantee that the number is 16 digits in length is to have it be formed as a string. Using this method I would recommend #rjmunro's answer:
number = (Math.random()+' ').substring(2,10)+(Math.random()+' ').substring(2,10);
Not with jQuery, no, but you can do it with plain javascript.
If you want exactly 16 digits (possibly including leading 0s), I would start with Math.random(), convert to a string, pick 8 digits, and concatenate 2 runs together.
number = (Math.random() + '').substring(2,10)
+ (Math.random() + '').substring(2,10);
No, use JAVASCRIPT!
jQuery is not some magic genie.
This is a task which is much better suited for raw javascript. For example
var str = '';
var i;
for (i = 0; i < 16; i++) {
var number = Math.floor(Math.random() * 10) % 10;
str += number;
}
I just tried with #rjmunro 's answer.
Unfortunately, it does generate string less than 16digits,
but very rare, approxly once in 10 million times.
Here is my testing code, runs in nodejs:
'use strict';
var fs = require('fs');
var totalTimes = 100000000;
var times = totalTimes;
var fileName;
var writeStream;
while (times > 0) {
var key = (Math.random() + ' ').substring(2,10) + (Math.random() + ' ').substring(2,10);
times --;
if (key.length !== 16) {
var msg = 'a flaw key gened: ' + key + '\n';
// create a log file at first time
if (!fileName) {
fileName = 'log/flaw_key_' + new Date() + '.txt';
}
writeStream = fs.createWriteStream(fileName);
writeStream.write(msg);
writeStream.end();
}
if (times === 0) {
console.log(totalTimes + ' times key gened');
}
}
Also #Dimitri Mikadze 's answer generate less length string as well, so I eventually adopt a way with some concept of his solution:
function getRandomInt(min, max) {
return Math.floor(Math.random() * (max - min + 1)) + min;
}
/**
* Gen random digits string in specific length
* #param {Int} length of string
*
* #return {String}
*
*/
function genString(length) {
var times = length;
var key = '';
while (times > 0) {
times --;
key += getRandomInt(0, 9);
}
return key;
}
genString(16); // a 16 digits string
u can use this function to generate random digits, just pass minimum and maximum parameters
function randomInt(min, max) {
return Math.floor(Math.random() * (max - min + 1) + min);
}
random 16 digit, usage
randomInt(0, 9999999999999999);
I know this question is old but this simple function will guarantee a 16 (or however many you want) character string every time without the 10% failure rate of other solutions. Can change it to a number if you need to.
function generate() {
let string = ""
while (string.length < 16) {
let number = Math.floor(Math.random() * 10).toString()
string += number
}
return string
}
I think this way is more beautiful:
const generateFixedLengthNumberInString = length =>
[...Array(length).keys()].reduce(
previousValue =>
previousValue + String(Math.floor(Math.random() * 10) % 10),
);
console.log(generateFixedLengthNumberInString(16))
// prints "0587139224228340"
The JavaScript Math.random() function returns a random value between 0 and 1, automatically seeded based on the current time (similar to Java I believe). However, I don't think there's any way to set you own seed for it.
How can I make a random number generator that I can provide my own seed value for, so that I can have it produce a repeatable sequence of (pseudo)random numbers?
One option is http://davidbau.com/seedrandom which is a seedable RC4-based Math.random() drop-in replacement with nice properties.
If you don't need the seeding capability just use Math.random() and build helper functions around it (eg. randRange(start, end)).
I'm not sure what RNG you're using, but it's best to know and document it so you're aware of its characteristics and limitations.
Like Starkii said, Mersenne Twister is a good PRNG, but it isn't easy to implement. If you want to do it yourself try implementing a LCG - it's very easy, has decent randomness qualities (not as good as Mersenne Twister), and you can use some of the popular constants.
EDIT: consider the great options at this answer for short seedable RNG implementations, including an LCG option.
function RNG(seed) {
// LCG using GCC's constants
this.m = 0x80000000; // 2**31;
this.a = 1103515245;
this.c = 12345;
this.state = seed ? seed : Math.floor(Math.random() * (this.m - 1));
}
RNG.prototype.nextInt = function() {
this.state = (this.a * this.state + this.c) % this.m;
return this.state;
}
RNG.prototype.nextFloat = function() {
// returns in range [0,1]
return this.nextInt() / (this.m - 1);
}
RNG.prototype.nextRange = function(start, end) {
// returns in range [start, end): including start, excluding end
// can't modulu nextInt because of weak randomness in lower bits
var rangeSize = end - start;
var randomUnder1 = this.nextInt() / this.m;
return start + Math.floor(randomUnder1 * rangeSize);
}
RNG.prototype.choice = function(array) {
return array[this.nextRange(0, array.length)];
}
var rng = new RNG(20);
for (var i = 0; i < 10; i++)
console.log(rng.nextRange(10, 50));
var digits = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'];
for (var i = 0; i < 10; i++)
console.log(rng.choice(digits));
If you want to be able to specify the seed, you just need to replace the calls to getSeconds() and getMinutes(). You could pass in an int and use half of it mod 60 for the seconds value and the other half modulo 60 to give you the other part.
That being said, this method looks like garbage. Doing proper random number generation is very hard. The obvious problem with this is that the random number seed is based on seconds and minutes. To guess the seed and recreate your stream of random numbers only requires trying 3600 different second and minute combinations. It also means that there are only 3600 different possible seeds. This is correctable, but I'd be suspicious of this RNG from the start.
If you want to use a better RNG, try the Mersenne Twister. It is a well tested and fairly robust RNG with a huge orbit and excellent performance.
EDIT: I really should be correct and refer to this as a Pseudo Random Number Generator or PRNG.
"Anyone who uses arithmetic methods to produce random numbers is in a state of sin."
--- John von Neumann
I use a JavaScript port of the Mersenne Twister:
https://gist.github.com/300494
It allows you to set the seed manually. Also, as mentioned in other answers, the Mersenne Twister is a really good PRNG.
The code you listed kind of looks like a Lehmer RNG. If this is the case, then 2147483647 is the largest 32-bit signed integer, 2147483647 is the largest 32-bit prime, and 48271 is a full-period multiplier that is used to generate the numbers.
If this is true, you could modify RandomNumberGenerator to take in an extra parameter seed, and then set this.seed to seed; but you'd have to be careful to make sure the seed would result in a good distribution of random numbers (Lehmer can be weird like that) -- but most seeds will be fine.
The following is a PRNG that may be fed a custom seed. Calling SeedRandom will return a random generator function. SeedRandom can be called with no arguments in order to seed the returned random function with the current time, or it can be called with either 1 or 2 non-negative inters as arguments in order to seed it with those integers. Due to float point accuracy seeding with only 1 value will only allow the generator to be initiated to one of 2^53 different states.
The returned random generator function takes 1 integer argument named limit, the limit must be in the range 1 to 4294965886, the function will return a number in the range 0 to limit-1.
function SeedRandom(state1,state2){
var mod1=4294967087
var mul1=65539
var mod2=4294965887
var mul2=65537
if(typeof state1!="number"){
state1=+new Date()
}
if(typeof state2!="number"){
state2=state1
}
state1=state1%(mod1-1)+1
state2=state2%(mod2-1)+1
function random(limit){
state1=(state1*mul1)%mod1
state2=(state2*mul2)%mod2
if(state1<limit && state2<limit && state1<mod1%limit && state2<mod2%limit){
return random(limit)
}
return (state1+state2)%limit
}
return random
}
Example use:
var generator1=SeedRandom() //Seed with current time
var randomVariable=generator1(7) //Generate one of the numbers [0,1,2,3,4,5,6]
var generator2=SeedRandom(42) //Seed with a specific seed
var fixedVariable=generator2(7) //First value of this generator will always be
//1 because of the specific seed.
This generator exhibit the following properties:
It has approximately 2^64 different possible inner states.
It has a period of approximately 2^63, plenty more than anyone will ever realistically need in a JavaScript program.
Due to the mod values being primes there is no simple pattern in the output, no matter the chosen limit. This is unlike some simpler PRNGs that exhibit some quite systematic patterns.
It discards some results in order to get a perfect distribution no matter the limit.
It is relatively slow, runs around 10 000 000 times per second on my machine.
Bonus: typescript version
If you program in Typescript, I adapted the Mersenne Twister implementation that was brought in Christoph Henkelmann's answer to this thread as a typescript class:
/**
* copied almost directly from Mersenne Twister implementation found in https://gist.github.com/banksean/300494
* all rights reserved to him.
*/
export class Random {
static N = 624;
static M = 397;
static MATRIX_A = 0x9908b0df;
/* constant vector a */
static UPPER_MASK = 0x80000000;
/* most significant w-r bits */
static LOWER_MASK = 0x7fffffff;
/* least significant r bits */
mt = new Array(Random.N);
/* the array for the state vector */
mti = Random.N + 1;
/* mti==N+1 means mt[N] is not initialized */
constructor(seed:number = null) {
if (seed == null) {
seed = new Date().getTime();
}
this.init_genrand(seed);
}
private init_genrand(s:number) {
this.mt[0] = s >>> 0;
for (this.mti = 1; this.mti < Random.N; this.mti++) {
var s = this.mt[this.mti - 1] ^ (this.mt[this.mti - 1] >>> 30);
this.mt[this.mti] = (((((s & 0xffff0000) >>> 16) * 1812433253) << 16) + (s & 0x0000ffff) * 1812433253)
+ this.mti;
/* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
/* In the previous versions, MSBs of the seed affect */
/* only MSBs of the array mt[]. */
/* 2002/01/09 modified by Makoto Matsumoto */
this.mt[this.mti] >>>= 0;
/* for >32 bit machines */
}
}
/**
* generates a random number on [0,0xffffffff]-interval
* #private
*/
private _nextInt32():number {
var y:number;
var mag01 = new Array(0x0, Random.MATRIX_A);
/* mag01[x] = x * MATRIX_A for x=0,1 */
if (this.mti >= Random.N) { /* generate N words at one time */
var kk:number;
if (this.mti == Random.N + 1) /* if init_genrand() has not been called, */
this.init_genrand(5489);
/* a default initial seed is used */
for (kk = 0; kk < Random.N - Random.M; kk++) {
y = (this.mt[kk] & Random.UPPER_MASK) | (this.mt[kk + 1] & Random.LOWER_MASK);
this.mt[kk] = this.mt[kk + Random.M] ^ (y >>> 1) ^ mag01[y & 0x1];
}
for (; kk < Random.N - 1; kk++) {
y = (this.mt[kk] & Random.UPPER_MASK) | (this.mt[kk + 1] & Random.LOWER_MASK);
this.mt[kk] = this.mt[kk + (Random.M - Random.N)] ^ (y >>> 1) ^ mag01[y & 0x1];
}
y = (this.mt[Random.N - 1] & Random.UPPER_MASK) | (this.mt[0] & Random.LOWER_MASK);
this.mt[Random.N - 1] = this.mt[Random.M - 1] ^ (y >>> 1) ^ mag01[y & 0x1];
this.mti = 0;
}
y = this.mt[this.mti++];
/* Tempering */
y ^= (y >>> 11);
y ^= (y << 7) & 0x9d2c5680;
y ^= (y << 15) & 0xefc60000;
y ^= (y >>> 18);
return y >>> 0;
}
/**
* generates an int32 pseudo random number
* #param range: an optional [from, to] range, if not specified the result will be in range [0,0xffffffff]
* #return {number}
*/
nextInt32(range:[number, number] = null):number {
var result = this._nextInt32();
if (range == null) {
return result;
}
return (result % (range[1] - range[0])) + range[0];
}
/**
* generates a random number on [0,0x7fffffff]-interval
*/
nextInt31():number {
return (this._nextInt32() >>> 1);
}
/**
* generates a random number on [0,1]-real-interval
*/
nextNumber():number {
return this._nextInt32() * (1.0 / 4294967295.0);
}
/**
* generates a random number on [0,1) with 53-bit resolution
*/
nextNumber53():number {
var a = this._nextInt32() >>> 5, b = this._nextInt32() >>> 6;
return (a * 67108864.0 + b) * (1.0 / 9007199254740992.0);
}
}
you can than use it as follows:
var random = new Random(132);
random.nextInt32(); //return a pseudo random int32 number
random.nextInt32([10,20]); //return a pseudo random int in range [10,20]
random.nextNumber(); //return a a pseudo random number in range [0,1]
check the source for more methods.
Here is quite an effective but simple javascript PRNG function that I like to use:
// The seed is the base number that the function works off
// The modulo is the highest number that the function can return
function PRNG(seed, modulo) {
str = `${(2**31-1&Math.imul(48271,seed))/2**31}`
.split('')
.slice(-10)
.join('') % modulo
return str
}
I hope this is what you're looking for.
Thank you, #aaaaaaaaaaaa (Accepted Answer)
I really needed a good non-library solution (easier to embed)
so... i made this class to store the seed and allow a Unity-esque "Next" ... but kept the initial Integer based results
class randS {
constructor(seed=null) {
if(seed!=null) {
this.seed = seed;
} else {
this.seed = Date.now()%4645455524863;
}
this.next = this.SeedRandom(this.seed);
this.last = 0;
}
Init(seed=this.seed) {
if (seed = this.seed) {
this.next = this.SeedRandom(this.seed);
} else {
this.seed=seed;
this.next = this.SeedRandom(this.seed);
}
}
SeedRandom(state1,state2){
var mod1=4294967087;
var mod2=4294965887;
var mul1=65539;
var mul2=65537;
if(typeof state1!="number"){
state1=+new Date();
}
if(typeof state2!="number"){
state2=state1;
}
state1=state1%(mod1-1)+1;
state2=state2%(mod2-1)+1;
function random(limit){
state1=(state1*mul1)%mod1;
state2=(state2*mul2)%mod2;
if(state1<limit && state2<limit && state1<mod1%limit && state2<mod2%limit){
this.last = random;
return random(limit);
}
this.last = (state1+state2)%limit;
return (state1+state2)%limit;
}
this.last = random;
return random;
}
}
And then checked it with these... seems to work well with random (but queryable) seed value (a la Minecraft) and even stored the last value returned (if needed)
var rng = new randS(9005646549);
console.log(rng.next(20)+' '+rng.next(20)+' '+rng.next(20)+' '+rng.next(20)+' '+rng.next(20)+' '+rng.next(20)+' '+rng.next(20));
console.log(rng.next(20) + ' ' + rng.next(20) + ' ' + rng.last);
which should output (for everybody)
6 7 8 14 1 12 6
9 1 1
EDIT: I made the init() work if you ever needed to reseed, or were testing values (this was necessary in my context as well)
Note: This code was originally included in the question above. In the interests of keeping the question short and focused, I've moved it to this Community Wiki answer.
I found this code kicking around and it appears to work fine for getting a random number and then using the seed afterward but I'm not quite sure how the logic works (e.g. where the 2345678901, 48271 & 2147483647 numbers came from).
function nextRandomNumber(){
var hi = this.seed / this.Q;
var lo = this.seed % this.Q;
var test = this.A * lo - this.R * hi;
if(test > 0){
this.seed = test;
} else {
this.seed = test + this.M;
}
return (this.seed * this.oneOverM);
}
function RandomNumberGenerator(){
var d = new Date();
this.seed = 2345678901 + (d.getSeconds() * 0xFFFFFF) + (d.getMinutes() * 0xFFFF);
this.A = 48271;
this.M = 2147483647;
this.Q = this.M / this.A;
this.R = this.M % this.A;
this.oneOverM = 1.0 / this.M;
this.next = nextRandomNumber;
return this;
}
function createRandomNumber(Min, Max){
var rand = new RandomNumberGenerator();
return Math.round((Max-Min) * rand.next() + Min);
}
//Thus I can now do:
var letters = ['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'];
var numbers = ['1','2','3','4','5','6','7','8','9','10'];
var colors = ['red','orange','yellow','green','blue','indigo','violet'];
var first = letters[createRandomNumber(0, letters.length)];
var second = numbers[createRandomNumber(0, numbers.length)];
var third = colors[createRandomNumber(0, colors.length)];
alert("Today's show was brought to you by the letter: " + first + ", the number " + second + ", and the color " + third + "!");
/*
If I could pass my own seed into the createRandomNumber(min, max, seed);
function then I could reproduce a random output later if desired.
*/
OK, here's the solution I settled on.
First you create a seed value using the "newseed()" function. Then you pass the seed value to the "srandom()" function. Lastly, the "srandom()" function returns a pseudo random value between 0 and 1.
The crucial bit is that the seed value is stored inside an array. If it were simply an integer or float, the value would get overwritten each time the function were called, since the values of integers, floats, strings and so forth are stored directly in the stack versus just the pointers as in the case of arrays and other objects. Thus, it's possible for the value of the seed to remain persistent.
Finally, it is possible to define the "srandom()" function such that it is a method of the "Math" object, but I'll leave that up to you to figure out. ;)
Good luck!
JavaScript:
// Global variables used for the seeded random functions, below.
var seedobja = 1103515245
var seedobjc = 12345
var seedobjm = 4294967295 //0x100000000
// Creates a new seed for seeded functions such as srandom().
function newseed(seednum)
{
return [seednum]
}
// Works like Math.random(), except you provide your own seed as the first argument.
function srandom(seedobj)
{
seedobj[0] = (seedobj[0] * seedobja + seedobjc) % seedobjm
return seedobj[0] / (seedobjm - 1)
}
// Store some test values in variables.
var my_seed_value = newseed(230951)
var my_random_value_1 = srandom(my_seed_value)
var my_random_value_2 = srandom(my_seed_value)
var my_random_value_3 = srandom(my_seed_value)
// Print the values to console. Replace "WScript.Echo()" with "alert()" if inside a Web browser.
WScript.Echo(my_random_value_1)
WScript.Echo(my_random_value_2)
WScript.Echo(my_random_value_3)
Lua 4 (my personal target environment):
-- Global variables used for the seeded random functions, below.
seedobja = 1103515.245
seedobjc = 12345
seedobjm = 4294967.295 --0x100000000
-- Creates a new seed for seeded functions such as srandom().
function newseed(seednum)
return {seednum}
end
-- Works like random(), except you provide your own seed as the first argument.
function srandom(seedobj)
seedobj[1] = mod(seedobj[1] * seedobja + seedobjc, seedobjm)
return seedobj[1] / (seedobjm - 1)
end
-- Store some test values in variables.
my_seed_value = newseed(230951)
my_random_value_1 = srandom(my_seed_value)
my_random_value_2 = srandom(my_seed_value)
my_random_value_3 = srandom(my_seed_value)
-- Print the values to console.
print(my_random_value_1)
print(my_random_value_2)
print(my_random_value_3)