let str = "WhelloKitty"

let subStr1 = String(str.dropFirst())
print(subStr1) // helloKitty
let subStr2 = String(str.dropFirst(6))
print(subStr2) // Kitty

if let index = path.firstIndex(of: "?") {
    let paramStr = path[path.index(after: index)..<path.endIndex]
  	// paramStr:"/xxx/xxx?"
    print("paramStr is:\(String(paramStr.dropLast())")
  	// paramStr:"/xxx/xxx"

}

if let index = path.firstIndex(of: "?") {
    let paramStr = path[path.index(after: index)..<path.endIndex]
    print("paramStr is:\(paramStr)")
}

let subStr3 = String(str.dropLast())
print(subStr3) // WhelloKitt
let subStr4 = String(str.dropLast(5))
print(subStr4) // Whello

extension String {

    /// 通过URL中的query参数获取对应字典
    /// ?time=2020-04&name=张三 =》{"time": "2020-04", "name": "张三" }
    func getUrlParameters() -> [String: String]? {
        var params: [String: String] = [:]

        let array = self.components(separatedBy: "?")
        if array.count == 2 {
            let paramsStr = array[1]
            if paramsStr.count > 0 {
                let paramsArray = paramsStr.components(separatedBy: "&")
                for param in paramsArray {
                    let arr = param.components(separatedBy: "=")
                    if arr.count == 2 {
                        params[arr[0]] = arr[1]
                    }
                }
            }
        }

        return params
    }
  /// 处理千分符号
  /// 10000 => 10，000
    func thousandsNumber(content: Double) -> String {
        let format = NumberFormatter()
        format.numberStyle = .decimal
        format.usesGroupingSeparator = true
        format.groupingSeparator = ","
        format.groupingSize = 3
        guard let result = format.string(for: NSNumber(value: content)) else { return "" }
        return result
    }

}