9-2 字符集

 <script>
        //备选字符集
        /*
        [0-9]           \d
        [a-z]
        [A-Z]
        [A-z]
        */
       var str = "32313dhhhdgaggff";
       var reg = /\d/g;
       console.log(str.replace(reg,"*"))
    </script>

  <script>
        /*
        w [ 0-9a-zA-Z_]
        .表示所有的字符
        \s表示空格的意思
        */
       var a= "hellow_worder1245WS"
       console.log(a.replace(/\w/g,"*"))
       console.log(a.replace(/./g,"*"))
    </script>

 <script>
        var a = "hellow.word"
        var reg = /\./;
        console.log(a.replace(reg,"*"));
    </script>