<script>
//var a=/^(([0-9])|(1[0-2])|(2[0-3])):[0-5][0-9]$/
//alert(a.test("8:30"))
//var a=/^(([0-9])|(1[0-2])|(2[0-3])):[0-5][0-9]$/
//alert(a.test("0:00"))
//var a=/^(([0-9])|(1[0-2])|(2[0-3])):[0-5][0-9]$/
//alert(a.test("23:59"))
//var b="123.4"
//var c="123.4"
function mm(m){
alert(m.replace(/^((\d+?)(\.?)(\d+?))$/,function (a,b,c,d,e){ if(d=="."){ return c+"."+e.substr(0,1)}else{ return b}  }))
}
mm("123.4545")
mm("123")
</script>

------解决方案--------------------
<script>
var s="1，2，234，234.264234，1234.1234";
alert(s.replace(/(\.\d)\d+/ig,"$1") )//不要四舍五入的
alert(s.replace(/\d+\.\d+/ig,a))//要四舍五入的
function a(v){
return ((v*1).toFixed(1));
}

</script>