Utilities.js is a 'library' of generally useful functions not included in JavaScript standard libraries.

README.md

Utilities.js

Description...

Utilities.get_random_integer()

The Utilities.get_random_integer() function returns a pseudo-random integer number in the range [min, max] or [min, max), depending on its arguments.

Syntax

Utilities.get_random_integer(min, max, mode)

Parameters

min

A number.

Minimum value of the range from which the random integer is returned. Minimum value is always included in the range. Defaults to 0 if no value is given.

max

A number.

Maximum value the range from which the random integer is returned. Maximum value is included in the range in inclusive mode, but excluded in exclusive mode. Defaults to 1 if no value is given.

mode

A string. Either "inclusive" or "exclusive". Defines whether to include or exclude maximum value from the range from which an integer is returned.

Examples

Utilities.get_random_integer();                     // 0 - 1
Utilities.get_random_integer(0, 5);                 // 0 - 5
Utilities.get_random_integer(0, 5, "exclusive")     // 0 - 4

Utilities.js

var Utilities = function () {}

Utilities.get_random_integer = function (min, max, mode)
{
	// Get a random integer between min and max values either
	// excluding the max value or including it

	"use strict;"

	// If parameters are missing, assign default values
	if (min === undefined) { var min = 0; }				// min defaults to 0
	if (max === undefined) { var max = 1; }				// max defaults to 1
	if (mode === undefined) { var mode = "inclusive" }	// mode defaults to inclusive
	
	// Check that min < max as it should be
	if (min > max)
	{
		throw new RangeError("Min is larger than max");
	}

	// Convert min and max into suitable integer values
	min = Math.ceil(min);
	max = Math.floor(max);

	if (mode === "inclusive")
	{
		// Inclusive mode will include max value
		return Math.floor(Math.random() * (max - min + 1)) + min;
	}
	else if (mode === "exclusive")
	{
		// Exclusive mode will exclude max value
		return Math.floor(Math.random() * (max - min)) + min;
	}
	else
	{	
		// Throw an error if mode is not inclusive nor exclusive
		throw new SyntaxError("Unknown mode " + mode);
	}
}