while(iphoneid!==null){
            var iphoneid=prompt("请输入手机号码");
            if(isNaN(iphoneid)||iphoneid.length!=11){
                alert("手机号必须是11位纯数字");
            }else{
                break;
            }
        }
        var m=iphoneid.split("");
            m.splice(0,7,"*******");
        var s=m.join("");
        document.write(s);