JSFiddle - React, Tailwind, and code Playground

JavaScript

var items = [
   {
      "Id":{
         "LValue":1,
         "Value":1
      },
      "Date":{
         "LValue":"2013-10-17T00:00:00",
         "Value":"2013-10-24T00:00:00"
      },
      "User":{
         "LValue":508,
         "Value":507
      },
      "Comments":{
         "LValue":"This a test load",
         "Value":"This a test"
      },
      "Name":"John Doe",
      "IsDeleted":false
   }
];

var flattenedItems = items.map(function(x) {
    var flattened = { LValues: {} };
    for (var prop in x) {
        flattened[prop] = x[prop].Value;
        flattened.LValues[prop] = x[prop].LValue;
    };
    return flattened;
});
console.log(flattenedItems);
console.log(JSON.stringify(flattenedItems));