Quick Tip: Get a Random Number Within a Specified Range Using AS3

We often need to use a randomly generated number for certain situations; using Math.random() * n will usually do the trick, but it will only calculate a number from 0 to n. What if we need a number that doesn't give 0 as the minimum value? How can you generate a random number between 100 and 1000? I'll show you how to do it in this Quick Tip.

Final Result

This example demonstrates the function we'll be creating:

Step 1: Brief Overview

Using a function created in ActionScript 3, we will calculate a number between two values. These values will be passed as parameters and used with the Math class to generate a random number.

Step 2: Create a New File

Open Flash and create a new Flash File (ActionScript 3.0).

Step 3: Open the Actions Panel

Press Option + F9 or go to Window > Actions to open the Actions Panel.

Step 4: Function Declaration

Declare a Function and name it randomRange; this function will return the random number, so set the return type to Number.

function randomRange():Number 
{

Step 5: Set Parameters

Two parameters will be used to calculate the number.

• minNum: The minimum value to return
• maxNum: The maximum value to return

function randomRange(minNum:Number, maxNum:Number):Number 
{

Step 6: Write the Main Function

This is the function with the actual random number generator line. The power of Math is used to generate the number.

function randomRange(minNum:Number, maxNum:Number):Number 
{
	return (Math.floor(Math.random() * (maxNum - minNum + 1)) + minNum);
}

Step 7: How it Works

We have our random number generator function, but what does this function do?

Take a look at the following image to get a better idea:

In the image's example, if Math.random() was less than 0.5, the result would be 550.

Step 8: Test with a Trace

A simple way to test the function is to use a trace() function. See the code below:

function randomRange(minNum:Number, maxNum:Number):Number 
{
	return (Math.floor(Math.random() * (maxNum - minNum + 1)) + minNum);
}

trace(randomRange(10, 20)); //A number between 10 and 20

Step 9: Example

This is a working example, it uses a button to calculate the number and display it in a TextField.

/* The randomRange function */

function randomRange(minNum:Number, maxNum:Number):Number 
{
	return (Math.floor(Math.random() * (maxNum - minNum + 1)) + minNum);
}

/* The actions that will perform when the button is pressed */

function buttonAction(e:MouseEvent):void
{
	//An array will store the numbers in the textfield
	var n:Array = inputText.text.split(","); 	
	
	//Calculate the number based on the input, convert the result to a string
	//and send that string to the textfield
	generatedNumber.text = String(randomRange(n[0], n[1]));
}

//Add button's event listener
actionButton.addEventListener(MouseEvent.MOUSE_UP, buttonAction);

Conclusion

This is a basic example of how you can use this function; experiment and use it in your own projects!

Thanks for reading!