How-To: The Big ‘Rounding Numbers’ Guide in Actionscript

I wrote so i don’t forget anymore, maybe i’ll help some else with this aswell, its all about rounding numbers, decimals and precision digits in Actionscript.

In AS2 we could use the following to round of number:

Three decimals:

var yourNumber:Number = 23.263636453737383838383838;
yourNumber =  Math.round(yourNumber *1000)/1000;
// Outputs 23.263

Two decimals:

var yourNumber:Number = 23.263636453737383838383838;
yourNumber = Math.round(yourNumber *100)/100;
// Outputs 23.26

One decimal:

var yourNumber:Number = 23.263636453737383838383838;
yourNumber = Math.round(yourNumber *10)/10;
// Outputs 23.2

And if you want to do it even nicer you do would write a little function so you dont have to do it manually all the time:

function round(num:Number, precision:Number):Number
{
	var decimalPlaces:Number = Math.pow(10, precision);
	trace(Math.round(decimalPlaces * num) / decimalPlaces)
	return Math.round(decimalPlaces * num) / decimalPlaces;
}
round(2.5678, 2); // returns 2.56

In AS3 we would write:

function round(num:Number, precision:int):Number
{
	var decimalPlaces:Number = Math.pow(10, precision);
	trace(Math.round(decimalPlaces * num) / decimalPlaces)
	return Math.round(decimalPlaces * num) / decimalPlaces;
}
round(2.500078, 2);

Gives us back a different result, namely 2.5 because flash removes the zero at the end of decimal values. This is ok if we use this result to calulate with. But if we wanted to use the result of this function as a visual asset, to make use in a textfield for instance, then we have to re-write this function so that it returns a string (in this case 2.50).

function round(num:Number, precision:int):String {
	var intVal:Number = Math.floor(num);
	var finalLength : int = intVal.toString().length + 1 + precision;
	var baseString : String = num.toString().substr(0, finalLength);
	if(baseString.length == intVal.toString().length) {
		baseString += ".";
	}
	while(baseString.length < finalLength) {
		baseString += "0";
	}
	trace(baseString)
	return baseString;
}
round(2.500078, 3); // 2.500

This would return us 2.500.

Onother quick way to do this in AS3 is using the toFixed() method in the Number class.

Number(2.500078).toFixed(3));

So there you have it; three ways of rounding numbers in Actionscript

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