Save, Update & Delete function using REST Services in Hosted App

   //Common script for adding and updating list item
   //Paramaters Required
   //1) AppWebUrl
   //2) HostUrl
   //3) Listname
   //4) Metadata of List item to be saved
   //5) Item Id to be updated
   //For Save call function as below
   //saveitem(AppWebUrl,HostUrl,listName,metadata,function(ItemId,data)
   //{
   //ItemId -->Saved/Updated Item Id, Returns 0 if error
   //Data -->success data
   //});
   //for update call function as below
   // UpdateItem(AppWebUrl,HostUrl,listName,metadata,ItemIdtobeupdated,function(ItemId,data)
   //{
   //ItemId -->Saved/Updated Item Id, Returns 0 if error
   //Data -->success data
   //});
  
   //DeleteItem(AppWebUrl, HostWebUrl, ListName,ItemId,function(Success,data)
   //{
   //Success --> returns 0--> If Error or ItemId--> If Success
   //Data -->success data
   //});
   function saveitem(e, t, o, n, a) {
       var Saveexecutor = new SP.RequestExecutor(e);
       var r = e + "/_api/SP.AppContextSite(@target)/web/lists/getbytitle('" + o + "')/items?@target='" + t + "'";
       Saveexecutor.executeAsync({
           url: r,
           method: "POST",
           body: n,
           headers: {
               "content-type": "application/json; odata=verbose",
               accept: "application/json;odata=verbose"
           },
           contentType: "application/json",
           success: function(e) {
               var t = JSON.parse(e.body);
               a(t.d.Id,e)
           },
           error: function(e) {
               console.log(JSON.stringify(e.body)), a(0,e)
           }
       })
   }

   function UpdateItem(e, t, o, n, a, r) {
       var Saveexecutor = new SP.RequestExecutor(e);
       var c = e + "/_api/SP.AppContextSite(@target)/web/lists/getbytitle('" + o + "')/items(" + a + ")?@target='" + t + "'";
       Saveexecutor.executeAsync({
           url: c,
           method: "POST",
           body: n,
           headers: {
               Accept: "application/json;odata=verbose",
               "content-type": "application/json;odata=verbose",
               "X-HTTP-Method": "MERGE",
               "IF-MATCH": "*"
           },
           contentType: "application/json",
           success: function(e) {
               r(a,e)
           },
           error: function(e) {
               console.log(JSON.stringify(e.body)), r(0,e)
           }
       })
   }
  
   function DeleteItem(AppWebUrl, HostWebUrl, ListName,ItemId, callback) {
       
        var Saveexecutor = new SP.RequestExecutor(AppWebUrl);
       var c = AppWebUrl + "/_api/SP.AppContextSite(@target)/web/lists/getbytitle('" + ListName + "')/items(" + ItemId + ")?@target='" + HostWebUrl + "'";
       Saveexecutor.executeAsync({
           url: c,
           method: "POST",
           headers: {
               Accept: "application/json;odata=verbose",
               "content-type": "application/json;odata=verbose",
               "X-HTTP-Method": "DELETE",
               "IF-MATCH": "*"
           },
           contentType: "application/json",
           success: function(data) {
               callback(ItemId,data)
           },
           error: function(data) {
               console.log(JSON.stringify(data.body)), callback(0,data)
           }
       })
    }