$().SPServices is best for SOAP

SPServices is a great tool, really nice work, Marc Anderson (@sympmarc). It has been there all the time I have developed for SharePoint. But the fact that you work with XML and you must parse the attributes (!) was the reason why I prefered listdata.svc and Client Object Model, where you get objects in JSON or you have a nice API to get objects and their properties. But there is an area where SPServices are really the best tool: SharePoint Web Services which only understand SOAP like SocialDataService.asmx.

Three ways to get list items

Just a little comparison. We’ll retrieve Titles from Tasks list (Oppgaver in nb-no).
listdata.svc

$.getJSON("/_vti_bin/ListData.svc/Oppgaver()?$select=Tittel")
	.done(function(data){
	  var tasks = data.d.results;
		for(var t in tasks) {
			var title = tasks[t].Tittel;
			console.log(title);
		}
	})
	.fail(function() {
		console.log("error");
	});

Pay attention to the field name: Tittel. I think it is the biggest shortcoming of listdata.svc: the fact that we can’t use the internal (static) field names.
Client Object Model

var ctx = SP.ClientContext.get_current();
var web = ctx.get_web();
var taskList = web.get_lists().getByTitle("Oppgaver");
var query = new SP.CamlQuery("<ViewFields><FieldRef Name='Title' /></ViewFields>");
var tasks = taskList.getItems(query);
ctx.load(tasks);
ctx.executeQueryAsync(function() {
	var listEnumerator = tasks.getEnumerator();
	while(listEnumerator.moveNext()) {
		var task = listEnumerator.get_current();
		var title = task.get_item("Title");
		console.log(title);
	}
}, function() {
	console.log("error");
});

SPServices

$().SPServices({
    operation: "GetListItems",
    async: true,
    listName: "Oppgaver",
    CAMLViewFields: "<ViewFields><FieldRef Name='Title' /></ViewFields>",
    completefunc: function (xData, Status) {
        $(xData.responseXML).SPFilterNode("z:row").each(function() {
            console.log( $(this).attr("ows_Title") );        
        });
    }
});

SPServices and SocialDataService

Let’s try to find the count of comments for an url. To do so we must create a SOAP envelope in javascript, send it and handle the response result:

var strUrl = "http://dev/Sider/Help.aspx";
var request = "<soap:Envelope \
    xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' \
    xmlns:xsd='http://www.w3.org/2001/XMLSchema' \
    xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'> \
    <soap:Body>    \
      <CountCommentsOnUrl \
          xmlns='http://microsoft.com/webservices/SharePointPortalServer/SocialDataService'> \
        <url>" + strUrl + "</url> \
      </CountCommentsOnUrl> \
     </soap:Body> \
  </soap:Envelope>";

jQuery.ajax({
  type: "POST",
  async: true,
  url: '/_vti_bin/SocialDataService.asmx?op=CountCommentsOnUrl',
  data: request,
  contentType: "text/xml; charset=utf-8",
  dataType: "xml",
  success: function (content, txtFunc, xhr) {
    var count = jQuery(content).find('CountCommentsOnUrlResult').text();
    console.log(count);
  }
});

It works but, we have to handle the creating of SOAP envelope in our javascript code which can be error prone. SPServices provides a nice abstraction layer and handles many scenarios. The same operation in SPServices:

$().SPServices({
  operation: "CountCommentsOnUrl",
  async: true,
  url:"http://dev/Sider/Help.aspx",
  completefunc: function (xData, Status) {
    var result = $(xData.responseXML).find("CountCommentsOnUrlResult")[0];
    console.log($(result).text());
  }
});

In both cases we have to iterate through responseXML. This is a sample responseXML for CountCommentsOnUrl from SocialDataService.asmx:

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope
  xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <soap:Body>
      <CountCommentsOnUrlResponse
          xmlns="http://microsoft.com/webservices/SharePointPortalServer/SocialDataService">
      <CountCommentsOnUrlResult>1</CountCommentsOnUrlResult>
    </CountCommentsOnUrlResponse>
  </soap:Body>
</soap:Envelope>