How to get deferred object for sharepoint rest queries

Question

I want to create one common jquery library to work with REST queries in sharepoint. I have two files.

1. REST_Operations.js
2. consumer.js

In REST_Operations.js I am writing rest queries with deferred object as follows.

"use strict";
var RESTQueries = RESTQueries || {};
RESTQueries.getItemsFromList = function(){
    var deferred = $.Deferred();
    var execute = function(){
        $.ajax({
            url:"https://mysiteurl/sites/practice/_api/web/lists/getByTitle('Pages')/items",
            method:'GET',
            headers:{Accept:'application/json; odata=verbose'},
            success:function(data){
                deferred.resolve(data);
            },
            error:function(err){
                deferred.reject(err);
            }
        });
        return deferred;
    };

    return {
        execute:execute
    }
}();

RESTQueries.readItemsFromList = function(){
    RESTQueries.getItemsFromList.execute().promise().then(function(data){
        return data;    
    });

}

If i put console.log in then() function, data is coming properly. I have one more js file, cosumer.js, in that i am calling readItemsFromList as follows

var items = RESTQueries.readItemsFromList();

so my idea is items variable should contain the json object or result for the rest query. But if i put console.log(items), output is coming as undefined. How to get the json object in the items variable?

If I try with following code

RESTQueries.readItemsFromList = function(siteUrl,listName){
    return (RESTQueries.getItemsFromList.execute(siteUrl,listName).promise().then(function(data){
            console.log(data);
           return data; 
    }));
}

it is giving me different kind of object. Find the below screenshot.

Answer 1

Add return in front off RESTQueries.getItemsFromList, like this:

RESTQueries.readItemsFromList = function(){
    return RESTQueries.getItemsFromList.execute().promise().then(function(data){
        return data;    
    });
}

Answer 2

I have one question, you are developing for APP in office 365 ?

If yes, continue reading the post. If not, explain to me how you want to do that maybe will help you :)

I'm sure you must put the AJAX that runs synchronously.

try with this code below:

"use strict";

var hostUrl = decodeURIComponent(getQueryStringParameter("SPHostUrl"));
var AppUrl = decodeURIComponent(getQueryStringParameter("SPAppWebUrl"));
var par_url, par_list; // parameters to set in ajax;
function getItemsFromList(){
    var deferred = $.Deferred();
        $.ajax({
            url: String.format("{0}/_api/sp.appcontextsite(@target)/web/lists/getByTitle('{1}')/items?@target='{3}'", AppUrl, par_list, par_url); 
            method:'GET',
            headers:{Accept:'application/json; odata=verbose'},
            success:function(data){
                deferred.resolve(data);
            },
            error:function(err){
                deferred.reject(err);
            }
        });
        return deferred;

};

function readItemsFromList(url, page){
  var scriptbase = hostUrl + "/_layouts/15/";
  // allow cross-domain between host and app!
  $.getScript(scriptbase + "SP.RequestExecutor.js", function () {
    par_url = url;
    par_page = page;
    var processGETitems = new getItemsFromList();
    processGETitems.done(function (result) {
            return result;
    });
    processGETitems.fail(function (result) {
            return result;
    });
  });   
}


function getQueryStringParameter(urlParameterKey) {
    var params = document.URL.split('?')[1].split('&');
    for (var i = 0; i < params.length; i = i + 1) {
        var singleParam = params[i].split('=');
        if (singleParam[0] == urlParameterKey) return decodeURIComponent(singleParam[1]);
    }
}

And now, you can call the method:

var items = getItemsFromList('http://yourdomain.com','ListName'); //return [Object] if not, maybe your url or list not exist.

Please let know if I helped you.

Thanks, b1c10

References: http://weshackett.com/2014/02/sp-requestexecutor-cross-domain-calls-using-rest-gotcha/

Note: If you use domain sphost different of hosturl that you set, you will get acess denied by security do Office 365 ! :/