Dollar functions

gistfile1.js

Number.prototype.asDollar = function()
{
    return "$" + this.toFixed(2);    
}

Number.prototype.asDollarWithCommas = function()
{
    var as_str  = this.toFixed(2),
        matches = as_str.match(/\.\d+$/),
        cents   = (matches && matches[0]),
        dollars = [],
        slice;

    as_str = as_str.replace(cents, '');
    while (as_str.length > 3){
        dollars.push(slice = as_str.slice(-3));
        as_str = as_str.replace(slice, '');
    }
    if (as_str.length){ dollars.push(as_str); }

    return "$" + dollars.reverse().join(',') + cents;
}