bad request error in the following code in REST API

Question

Hi all,

           I am develping Sharepoint hosted app using REST API.In that i am adding client webpart.I can't access the host web resources.the error is coming as bad request.Please tell me what mistake i am doing in the below code.Thanks in advance.

<script type="text/javascript">
       var hostweburl;
       var appweburl;
       $(document).ready(function () {
           debugger;
           //Get the URI decoded URLs.
           //hostweburl = decodeURIComponent(getQueryStringParameter("SPHostUrl"));
           //appweburl = decodeURIComponent(getQueryStringParameter("SPAppWebUrl")
           hostweburl = _spPageContextInfo.siteAbsoluteUrl;
           appweburl = _spPageContextInfo.webAbsoluteUrl;
           // resources are in URLs in the form:
           // web_url/_layouts/15/resource
           var scriptbase = hostweburl + "/_layouts/15/";
           // Load the js files and continue to the successHandler
           $.getScript(scriptbase + "SP.RequestExecutor.js", getListsFromRootSite);


       })


       function getListsFromRootSite() {
           try {
               debugger;
               var executor = new SP.RequestExecutor(appweburl);
               executor.executeAsync(
               //jQuery.ajax({
               {
                   url: appweburl + "/_api/SP.AppContextSite('" + hostweburl + "')/Web/lists?$filter=BaseTemplate eq 101&$expand=RootFolder",
                   method: "GET",
                   headers: {
                       "Accept": "application/json; odata=verbose"
                   },
                   async: false,
                   success: function (data) {
                       debugger;
                       var lists = data.d.results;
                       var tempValue = "<span style='text-align:center;display:block;font-size:16px;color:#000;font-weight:bold;'>General Folders</span><br/><br/>";
                       tempValue += "<table id='tabledocuments' cellpadding='5' cellspacing='5' style='background-color:#f4f4f4'>";
                       lists.forEach(function (list) {
                           var itemCount = getDocumentLibrariesItemsCount(_spPageContextInfo.webAbsoluteUrl, list.Title);
                           if (!window.location.origin) {
                               window.location.origin = window.location.protocol + "//" + window.location.hostname + (window.location.port ? ':' + window.location.port : '');
                           }
                           var libraryURL = window.location.origin + list.RootFolder.ServerRelativeUrl;
                           console.log("Document URL= " + libraryURL);
                           tempValue += "<tr><td><a style='color:#000;text-decoration:none' href='" + libraryURL + "'>" + list.Title + " (" + itemCount + ")</a></td></tr>";
                       });
                       tempValue += "</table>";
                       $("#divRootSiteLibraries").html(tempValue);
                       getSubsites();
                   },
                   error: function (data) {
                       console.log(data);
                   }
               });
               //)
           } catch (e) {
               console.log(e);
           }
       }

       function getDocumentLibrariesItemsCount(webURL, listTitle) {
           var itemCount;
           try {
               jQuery.ajax({
                   url: webURL + "/_api/SP.AppContextSite(@target)/Web/lists/getByTitle('" + listTitle + "')?$select=ItemCount",
                   method: "GET",
                   headers: {
                       "Accept": "application/json; odata=verbose"
                   },
                   async: false,
                   success: function (data) {
                       itemCount = data.d.ItemCount;
                   },
                   error: function (data) {
                       console.log(data);
                   }
               });
               return itemCount;
           }
           catch (e) {
               console.log(e);
           }
       }

       function getDocumentLibrariesCount(webURL) {
           var libraryCount;
           try {
               jQuery.ajax({
                   url: webURL + "/_api/SP.AppContextSite(@target)/Web/lists?$filter=BaseTemplate eq 101",
                   method: "GET",
                   headers: {
                       "Accept": "application/json; odata=verbose"
                   },
                   async: false,
                   success: function (data) {
                       debugger
                       libraryCount = data.d.results.length;
                   },
                   error: function (data) {
                       console.log(data);
                   }
               });
               return libraryCount;
           }
           catch (e) {
               console.log(e);
           }
       }

       function getSubsites() {
           try {
               jQuery.ajax({
                   url: appweburl + "/_api/SP.AppContextSite(@target)/Web/GetSubwebsFilteredForCurrentUser(nWebTemplateFilter=-1)?$filter=WebTemplate ne 'APP'",
                   method: "GET",
                   headers: {
                       "Accept": "application/json; odata=verbose"
                   },
                   async: false,
                   success: function (data) {
                       var icount = 1;
                       var subSites = data.d.results;
                       console.log(subSites);
                       var tempValue = "<span style='text-align:center;display:block;font-size:14px;color:#000;font-weight:bold;'>Management Lines</span><br/><br/>";
                       tempValue += "<table style='display:inline-block;border:none;' cellpadding='5' cellspacing='5' style='background-color:#f4f4f4'>";
                       subSites.forEach(function (site) {
                           debugger;
                           if (!window.location.origin) {
                               window.location.origin = window.location.protocol + "//" + window.location.hostname + (window.location.port ? ':' + window.location.port : '');
                           }
                           var webURL = window.location.origin + site.ServerRelativeUrl;
                           var librariesCount = getDocumentLibrariesCount(webURL);
                           if (icount == 1)
                               tempValue += "<tr>";
                           tempValue += "<td><table id='tableSubsites' cellpadding='5' cellspacing='5' style='margin:20px;margin-top:0px;text-align:center;display:inline-block'>" +
                               "<tr style='font-weight:bold;background-color:#ffffff;'><td style='padding-left:20px;padding-right:20px;'>" + site.Title + "</td></tr>";
                           tempValue += "<tr style='background-color:#f4f4f4;'><td style='padding-left:20px;padding-right:20px;'><a style='color:#000;text-decoration:none;' href='" + webURL + "'>Active Issuers (" + librariesCount + ")</a></td></tr></table></td>";
                           var remainder = icount % 4;
                           if (remainder == 0)
                               tempValue += "</tr>";
                           icount++;
                       });
                       tempValue += "</table>";
                       $("#divSubSites").html(tempValue);
                   },
                   error: function (data) {
                       console.log(data);
                   }
               });
           } catch (e) {
               console.log(e);
           }
       }

       // Function to retrieve a query string value.
       // For production purposes you may want to use
       //  a library to handle the query string.
       function getQueryStringParameter(paramToRetrieve) {
           var params =
               document.URL.split("?")[1].split("&");
           var strParams = "";
           for (var i = 0; i < params.length; i = i + 1) {
               var singleParam = params[i].split("=");
               if (singleParam[0] == paramToRetrieve)
                   return singleParam[1];
           }
       }
   </script>