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

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Created by:

Walter

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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

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/*
    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