/^(?:(\d+\.)(\d\d)())$/
匹配2位小数的数字
:? 非捕获性分组就是分组中不再捕获(\d+.)(\d\d)() 这个组，你可以自己对比下分组结果
/^(?:(\d+\.)(\d\d)())$/.exec(11.21) ["11.21", "11.", "21", ""] /^((\d+\.)(\d\d)())$/.exec(11.21) ["11.21", "11.21", "11.", "21", ""]
反向引用带两个小数点的正数