Cookbooks
Google Apps Script
Chapter 3. Numbers
Generating random numbers

Google Apps Script:
Generating random numbers

How to:

In Google Apps Script, you can generate random numbers using the Math.random() function, similar to JavaScript. This function returns a floating-point, pseudo-random number in the range 0 (inclusive) to 1 (exclusive). To tailor these numbers for various use cases, such as generating integers within a specific range, you may need to perform additional calculations.

Generating a Basic Random Number

To generate a simple random number and log it to the console:

function generateRandomNumber() {
  var randomNumber = Math.random();
  Logger.log(randomNumber);
}

Sample output: 0.1234567890123456

Generating an Integer within a Specific Range

To generate a random integer between two values (min and max), inclusive:

function getRandomInt(min, max) {
  min = Math.ceil(min);
  max = Math.floor(max);
  var randomNumber = Math.floor(Math.random() * (max - min + 1)) + min;
  Logger.log(randomNumber);
  return randomNumber;
}

// Example:
getRandomInt(1, 10);

Sample output: 7

Remember, the Math.ceil() function is used to round the minimum value up, and Math.floor() is used to round the maximum value down, ensuring the random number is within the specified range.

Deep Dive

The mechanism for generating random numbers in Google Apps Script, and indeed in most programming languages, utilizes a pseudo-random number generator (PRNG). This technique is deterministic and relies on an initial value, known as the seed, to produce a sequence of numbers that appears random. While sufficient for many applications, it’s important to note that pseudo-random numbers may not be appropriate where high security or true randomness is required, such as in cryptographic applications.

True randomness can be achieved through hardware random number generators or services that generate randomness from natural phenomena. However, for most day-to-day scripting needs in Google Apps Script, Math.random() suffices.

Historically, the quest for more effective random number generation techniques has led to the development of various algorithms, with notable examples being the Mersenne Twister and Linear Congruential Generator (LCG). However, given the high level of abstraction in Google Apps Script, most users won’t need to implement these algorithms directly but understanding the underlying principles can help in appreciating the importance and limitations of random number generation in your scripts.

Rounding numbers