JavaScript - generate random long value as string (without BigInt usage)

In this short article, we would like to show how in simple way generate random long value as string using JavaScript.

Note: as long value we understand signed 64 bits integer value (from -9223372036854775808 to 9223372036854775807).

Quick solution:

// ONLINE-RUNNER:browser;

const randomNumber = (min, max) => {
    const scope = max - min + 1;
    return Math.floor(min + scope * Math.random());
};

const randomString = (min, max, length = 0) => {
    let text = String(randomNumber(min, max));
    for (let i = text.length; i < length; ++i) {
        text = '0' + text;
    }
    return text;
};

const randomLong = () => {
    //
    // - 922337203685477 5808    <--- min long value (int64)
    // + 922337203685477 5807    <--- max long value (int64)
    //   AAAAAAAAAAAAAAA BBBB
    //
    //   A - part 1
    //   B - part 2
    //
    const a = randomNumber(-922337203685477, +922337203685477);
    if (a < 0) {
        return a + randomString(0, a > -922337203685477 ? 10000 : 5808, 4);
    } else {
        return a + randomString(0, a < +922337203685477 ? 10000 : 5807, 4);
    }
};


// Usage example:

console.log(randomLong());  // -6733751053698669900
console.log(randomLong());  //  -682370853513783837
console.log(randomLong());  //  5592452255720332045

Note: the above solution doesn't use BigInt type that makes it working in the older JavaScript engines.

See also

1. JavaScript - random long value