String Range 截取
let str = "jafldkjakldjf&bgColor=#ff540d&step=4"
let range = str?.range(of: "bgColor=")
let startIndex = urlStr?.index(range!.upperBound, offsetBy:1)
let endIndex = urlStr?.index(range!.upperBound, offsetBy:6)
let colorStr = urlStr![startIndex! ..< endIndex!]
debugPrint(colorStr)