Javascript converts numbers into currency format strings

The first method here is to use JavaScript to convert the number number to the format of the currency string (parameters: reserve decimal places, currency symbols, integer parts thousands separator, decimal separator)

The second method here is to convert a currency character to a pure numeric string using a simple regular expression, then you can convert the string to a numeric number
JavaScript Money Format (Extending Number with prototype)

// Extend the default Number object with a formatMoney() method:
// usage: someVar.formatMoney(decimalPlaces, symbol, thousandsSeparator, decimalSeparator)
// defaults: (2, "$", ",", ".")
Number.prototype.formatMoney = function (places, symbol, thousand, decimal) {
  places = !isNaN(places = Math.abs(places)) ? places : 2;
  symbol = symbol !== undefined ? symbol : "$";
  thousand = thousand || ",";
  decimal = decimal || ".";
  var number = this,
    negative = number < 0 ? "-" : "",
    i = parseInt(number = Math.abs(+number || 0).toFixed(places), 10) + "",
    j = (j = i.length) > 3 ? j % 3 : 0;
  return symbol + negative + (j ? i.substr(0, j) + thousand : "") + i.substr(j).replace(/(\d{3})(?=\d)/g, "$1" + thousand) + (places ? decimal + Math.abs(number - i).toFixed(places).slice(2) : "");
};

Here are a few examples of transformations:

// Default usage and custom precision/symbol :
var revenue = 12345678;
alert(revenue.formatMoney()); // $12,345,678.00
alert(revenue.formatMoney(0, "HK$ ")); // HK$ 12,345,678

// European formatting:
var price = 4999.99;
alert(price.formatMoney(2, " � , ".", ",")); //  � .999,99

// It works for negative values, too:
alert((-500000).formatMoney(0, "£ ")); // £ -500,000

Currency to number removing money formatting (filtered by regular expressions)

var price = (12345.99).formatMoney(); // "$12,345.99"

// Remove non-numeric chars (except decimal point/minus sign):
priceVal = parseFloat(price.replace(/[^0-9-.]/g, '')); // 12345.99

This method only applies to patterns where the decimal separator is "." If the decimal separator is "," then the regular expression is /[^0-9-,]/g

Extended versions of Number without prototype:

// To set it up as a global function:
function formatMoney(number, places, symbol, thousand, decimal) {
  number = number || 0;
  places = !isNaN(places = Math.abs(places)) ? places : 2;
  symbol = symbol !== undefined ? symbol : "$";
  thousand = thousand || ",";
  decimal = decimal || ".";
  var negative = number < 0 ? "-" : "",
    i = parseInt(number = Math.abs(+number || 0).toFixed(places), 10) + "",
    j = (j = i.length) > 3 ? j % 3 : 0;
  return symbol + negative + (j ? i.substr(0, j) + thousand : "") + i.substr(j).replace(/(\d{3})(?=\d)/g, "$1" + thousand) + (places ? decimal + Math.abs(number - i).toFixed(places).slice(2) : "");
}

// To create it as a library method:
myLibrary.formatMoney = function (number, places, symbol, thousand, decimal) {
  /* as above */
}

// Example usage:
formatMoney(54321); // $54,321
myLibrary.formatMoney(12345, 0, "£ "); // £ 12,345