1. // num-数字 places-保留几位小数 symbol-货币符号
    2. numberTocurrency(num, places, symbol) {
    3.   Number.prototype.formatMoney = function (places, symbol, thousand, decimal) {
    4.     places = !isNaN(places = Math.abs(places)) ? places : 2;
    5.     symbol = symbol !== undefined ? symbol : "$";
    6.     thousand = thousand || ",";
    7.     decimal = decimal || ".";
    8.     var number = this,
    9.         negative = number < 0 ? "-" : "",
    10.         i = parseInt(number = Math.abs(+number || 0).toFixed(places), 10) + "",
    11.         j = (j = i.length) > 3 ? j % 3 : 0;
    12.     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) : "");
    13.   };
    14.   return parseFloat(num).formatMoney(places, symbol);
    15. }