JavaScript - random integer number in range with exclusive max value example

In this article, we would like to show you how to randomize integer numbers in a range with an exclusive max value in JavaScript.

1. Custom random method examples

// ONLINE-RUNNER:browser;

/*
	inclusive min (result can be equal to min value)
    exclusive max (result will not be to max value)
*/
function randomizeInteger(min, max) {
  	if(max == null) {
    	max = (min == null ? Number.MAX_SAFE_INTEGER : min);
      	min = 0;
    }

    min = Math.ceil(min);  // inclusive min
    max = Math.floor(max); // exclusive max

  	if(min > max - 1) {
    	throw new Error("Incorrect arguments.");
    }

    return min + Math.floor((max - min) * Math.random());
}

// Example:

console.log(randomizeInteger()); // 5547382624322139
console.log(randomizeInteger(5)); // 3
console.log(randomizeInteger(10, 80)); // 62
console.log(randomizeInteger(-50, 50)); // -8

See also

1. JavaScript - Math.random() method example