Recipe 5.6 Formatting Currency Amounts

5.6.1 Problem

You want to format a number as currency, such as dollars.

5.6.2 Solution

Create a custom Math.currencyFormat( ) method.

5.6.3 Discussion

Unlike some other languages, such as ColdFusion, ActionScript does not have a built-in function for formatting numbers as currency amounts. That's the bad news. The good news is that it is not too difficult to create a custom method to format numbers as currency amounts.

Our custom Math.currencyFormat( ) method accepts up to seven parameters:

num

The number to format.

decimalPl

The number of decimal places in the formatted number.

currencySymbol

The symbol, such as a dollar sign ($), to use.

thousandsDelim

The characters used to delimit thousands, millions, etc.

decimalDelim

The characters used to delimit the fractional portion from the whole number.

truncate

If true, truncate the number to the specified number of decimal places; otherwise, round the number.

spaceFill

The number of spaces the entire formatted string should occupy.

Here is our custom Math.currencyFormat( ) method. The method converts a numeric parameter into a currency-formatted string. Include this method within Math.as along with the custom roundDecPl( ), numberFormat( ), and zeroFill( ) methods in this chapter, on which this example relies.

Math.currencyFormat = function (num, decimalPl, currencySymbol, thousandsDelim,
                                decimalDelim, truncate, spaceFill) {

  // Default to two decimal places, a dollar sign ($), a comma for thousands, and a 
  // period for the decimal point. We implemented the defaults using the conditional
  // operator. Compare with Recipe 5.5.
  decimalPl      = (decimalPl == undefined)      ? 2   : decimalPl;
  currencySymbol = (currencySymbol == undefined) ? "$" : currencySymbol;
  thousandsDelim = (thousandsDelim == undefined) ? "," : thousandsDelim;
  decimalDelim   = (decimalDelim == undefined)   ? "." : decimalDelim;

  // Split the number into the whole and decimal (fractional) portions.
  var parts = String(num).split(".");

  // Truncate or round the decimal portion, as directed.
  if (truncate) {
    parts[1] = Number(parts[1]) * Math.pow(10, -(decimalPl - 1));
    parts[1] = String(Math.floor(parts[1]));
  } else {
    // Requires the roundDecPl(  ) method defined in Recipe 5.3
    parts[1] = Math.roundDecPl(Number("." + parts[1]), decimalPl);
    parts[1] = String(parts[1]).split(".")[1];
  }

  // Ensure that the decimal portion has the number of digits indicated. 
  // Requires the zeroFill(  ) method defined in Recipe 5.4.
  parts[1] = Math.zeroFill(parts[1], decimalPl, true);
  
  // If necessary, use the numberFormat(  ) method from Recipe 5.5 to format the number
  // with the proper thousands delimiter and leading spaces.
  if (thousandsDelim != "" || spaceFill != undefined) {
    parts[0] = Math.numberFormat(parts[0], thousandsDelim, "",
                spaceFill - decimalPl - currencySymbol.length);
  }

  // Add a currency symbol and use String.join(  ) to merge the whole (dollar) and
  // decimal (cents) portions using the designated decimal delimiter.
  return currencySymbol + parts.join(decimalDelim);
};

Here are a few examples of Math. currencyFormat ( ) in action:

trace(Math.currencyFormat(1.2));                    // Displays: $1.20
trace(Math.currencyFormat(.3));                     // Displays: $0.30
trace(Math.currencyFormat(1234567));                // Displays: $1,234,567.00
trace(Math.currencyFormat(12.34, 2, "\u20AC"));     // Displays: 12.34 (euros)
trace(Math.currencyFormat(12.34, 2, "\u00a3"));     // Displays: £12.34 (pounds)
trace(Math.currencyFormat(12.34, 2, "\u00a5"));     // Displays: ¥12.34 (yen)
trace(Math.currencyFormat(1.2, 2, "", ".", ","));   // Displays: 1,20
trace(Math.currencyFormat(1234, 2, "", ".", ","));  // Displays: 1.234,00

5.6.4 See Also

Recipe 5.3 and Recipe 5.5. See Appendix A for creating special characters, including the euro, yen, and British pound symbols. To align currency amounts in text fields, use a monospaced font and set the field's format to right justification using the TextFormat.align property.