Javascript Random Integer Between two Numbers

Question

I'm trying to create a random number generator that generates random numbers between two numbers. For instance, let's say I want to generate a random number between 4 and 10, I would want it to be able to choose from any number from 4 - 10. Here is what I tried:

var randNumMin = 4; var randNumMax = 10; var randInt = (Math.floor(Math.random() * (randNumMax - randNumMin + 1)) + randNumMin); 

However, that didn't seem to work and generated weird random numbers that weren't between 4 and 10, and some began with 0. What would be the correct algorithm to do this?

Here is the code I'm implementing the algorithm in:

$(function() {     $('#generateRandNums').click(function() {          var numCount = document.getElementById("randNumCount").value;         var randNumMin = document.getElementById("randNumMin").value;         var randNumMax = document.getElementById("randNumMax").value;          if (numCount.match(/^[\d]*$/ ) && randNumMin.match(/^[\d]*$/ ) && randNumMax.match(/^[\d]*$/ )) {                    if (numCount == "" || randNumMin == "" || randNumMax == "")  {                 alert ("Please fill out all forms then try again.");              } else {                 if (randNumMin>randNumMax) {                     alert ("Please make sure your first number is smaller than the second, then try again.");                 } else {                     if (randNumMin<0) {                         alert ("Please make sure that you generate a positive number of random numbers, then try again.");                     } else {                          if (numCount>1) {                             var randResult = ("You generated " + numCount + " random numbers between " + randNumMin + " and " + randNumMax + " and got the numbers ")                             oneNumber = 0;                         } else {                             var randResult = ("You generated a random number between " + randNumMin + " and " + randNumMax + " and got the number ");                             oneNumber = 1;                         }                         for (i=0;i<numCount;i++) {                         //Get a random number between randNumMin and randNumMax                         var randInt = (Math.floor(Math.random() * (randNumMax - randNumMin + 1)) + randNumMin);                             if (i == numCount-1) {                                 if (oneNumber == 0) {                                     randResult = (randResult + "and " + randInt + ".");                                 } else {                                     randResult = (randResult + randInt + ".");                                 }                             } else {                                 randResult = (randResult + randInt + ", ");                             }                         }                         $("#randNumResults").val(randResult);                     }                 }             }         } else {             alert ("Make sure you only enter numbers and no spaces, then try again.");         }      }); }); 

I also tried replacing the randInt line with this:

var randInt = Math.floor((Math.random() * ((randNumMax + 1) - randNumMin)) + randNumMin); 

It still didn't work. I'm not sure if the algorithm is wrong or I'm incorporating it wrong into the function. An answer is appreciated, thanks.

Answer 1

Generating random whole numbers in JavaScript in a specific range?

/**  * Returns a random number between min and max  */ function getRandomArbitary (min, max) {     return Math.random() * (max - min) + min; }  /**  * Returns a random integer between min and max  * Using Math.round() will give you a non-uniform distribution!  */ function getRandomInt (min, max) {     return Math.floor(Math.random() * (max - min + 1)) + min; } 

http://roshanbh.com.np/2008/09/get-random-number-range-two-numbers-javascript.html

//function to get random number upto m function randomXToY(minVal,maxVal,floatVal) {     var randVal = minVal+(Math.random()*(maxVal-minVal));     return typeof floatVal=='undefined'?Math.round(randVal):randVal.toFixed(floatVal); } 

or

Generate random number between two numbers in JavaScript

Answer 2

Your problem is you never converted your string to numbers try adding this

if (  numCount.match(/^[\d]*$/ ) &&      randNumMin.match(/^[\d]*$/ ) &&      randNumMax.match(/^[\d]*$/ )){   if (numCount === "" || randNumMin === "" || randNumMax === "")  {     alert ("Please fill out all forms then try again.");   } else {     numCount=numCount-0;randNumMin=randNumMin-0;randNumMax=randNumMax-0; 

Another note you need to change your checking if the value is an empty string to strict equality. To see what I mean try using zero for one of the values. 0 == ""//returns true because both are falsy 0 === ""//returns false.