text: let string = {};
  
  // 对字符串加入间隔，间隔数量和间隔符号可自定义
  string.join_space = function(str, spaceNum = 4, space = ' ') {
    let result = '', counter = 0;
    for (let i = str.length - 1; i >= 0; i--) {
        counter++;
        result = str.charAt(i) + result;
        if (!(counter % spaceNum) && i != 0) {
            result = `${space}` + result;
        }
    }
    return result;
  }
  
  module.exports = string;