можно воспользоваться функцией наподобие этой: 
function number_format( number, decimals, dec_point, thousands_sep ) {  // Format a number with grouped thousands
    var i, j, kw, kd, km;
    if( isNaN(decimals = Math.abs(decimals)) ){
        decimals = 2;
    }
    if( dec_point == undefined ){
        dec_point = ",";
    }
    if( thousands_sep == undefined ){
        thousands_sep = ".";
    }
    i = parseInt(number = (+number || 0).toFixed(decimals)) + "";
    if( (j = i.length) > 3 ){
        j = j % 3;
    } else{
        j = 0;
    }
    km = (j ? i.substr(0, j) + thousands_sep : "");
    kw = i.substr(j).replace(/(\d{3})(?=\d)/g, "$1" + thousands_sep);
    kd = (decimals ? dec_point + Math.abs(number - i).toFixed(decimals).replace(/-/, 0).slice(2) : "");
    return km + kw + kd;
}