code: function stringRepeat (str, count) {
    var rest = '' + str
    if (str.repeat) {
      return str.repeat(count)
    }
    var list = isNaN(count) ? [] : new Array(parseInt(count))
    return list.join(rest) + (list.length > 0 ? rest : '')
  }
docs: 将字符串重复 n次
  
  @param {String} str 字符串
  @param {Number} count 次数
  @return {String}