JavaScript: How to generate an array of random numbers

/ Chris Nielsen

Let’s say I want to create a list of 10 numbers that are between the values of 0 and 1. This can be done with a simple for loop. For example:

let length = 10;
let max = 1;
let randArray = [];
for (i=0; i < length; i++) {
    randArray.push(Math.random(max));
}
console.log(randArray);

Setting the max value to 1 gives me only random values between 0 and 1. Setting the length to 10 gives me a list of 10 numbers.  This yields:

[0.515654184126071, 0.3903385797823882, 0.9408518825018701, 0.08469998671516599, 0.2765966591556014, 
0.20919957282624446, 0.9498787982265717, 0.5195513802386978, 0.7100803314063749, 0.03271176762225736]

Now instead of values between 0 and 1, lets say I want values from 1 to 100 and I want no decimals:

let length = 10;
let max = 100;
let randArray = [];
for (i=0; i < length; i++) {
 randArray.push(Math.round(Math.random() * max));
}
console.log(randArray);

Here I wrapped the Math.random() function in a Math.round() function (so there are no decimals), and multiplied each number by the max. The result is:

[75, 22, 66, 20, 24, 86, 66, 6, 59, 75]

For more information about Math.random(), see:
https://www.w3schools.com/jsref/jsref_random.asp
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random

For more information about Math.round(), see:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/round