typescript 数字转变为汉字大写

    /**根据数字获取汉字*/
    public changeToCN(num: number): string {
        let words = ["零", "一", "二", "三", "四", "五", "六", "七", "八", "九", "十"];
        let adds = ["", '十', '百', '千', '万', '亿', '十', '百', '千'];
        if(words[num]){
                return words[num];
        }
        else if(num > 10 && num < 20){
                let numStr = num.toString();
                let n = numStr.substring(1, 2);
                let result = adds[1] + words[n];
                return result;
        }
        else if(num > 10){
                let result = "";
                let numStr = num.toString();
                for (var i = 0; i < numStr.length; ++i) {
                        let n = numStr.substring(i, i+1);
                        let m = numStr.length - i - 1;
                        result += words[n] + adds[m];
                }
                return result;
        }
        else return "零";
    }