Hi I would like to generate a random number between -x and x in JavaScript. This is what I have :

function randomInt(nb){
let absoluteVal = Math.ceil(Math.random()*nb)
let sign = Math.floor(Math.random()*2)
return sign == 1 ? absoluteVal*(-1) : absoluteVal;
}
console.log(randomInt(4))

<iframe name="sif1" sandbox="allow-forms allow-modals allow-scripts" frameborder="0"></iframe>

It works but it is rather inelegant. I was wondering if somebody knew a better solution. Thanks in advance.

CodePudding user response：

For example with n = 4, it generates this values:

-4 -3 -2 -1  0  1  2  3  4

In total 9 elements. By using positive values, it generates 0 ... 8 with an ofset of -4.

function randomInt(n) {
    return Math.floor(Math.random() * (2 * n   1)) - n;
}

console.log(randomInt(4));
console.log(randomInt(4));
console.log(randomInt(4));
console.log(randomInt(4));
console.log(randomInt(4));
console.log(randomInt(4));
console.log(randomInt(4));
console.log(randomInt(4));

.as-console-wrapper { max-height: 100% !important; top: 0; }

<iframe name="sif2" sandbox="allow-forms allow-modals allow-scripts" frameborder="0"></iframe>

CodePudding user response：

Using Math.random() (returns a random number between 0 and 1) allows you to do it.

function randomInt(nb){
   return Math.ceil(Math.random() * nb) * (Math.round(Math.random()) ? 1 : -1)
}

console.log(randomInt(4));

<iframe name="sif3" sandbox="allow-forms allow-modals allow-scripts" frameborder="0"></iframe>