$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: '<%=ResolveClientUrl("~/WebServices/example.asmx/Method")%>',
data: "{'parameter1':'" + parametervalue1 + "'}",
dataType: "json",
async: false,
success: function (data) {alert(data.d);}
});
Reference: