改善js范围的最佳方法

Question

Hello everyone I'm trying to display some data when I make an HTTPRequest but when I call the function that retrieves a callback from the httprequets the scope of the function wont let me get to the data I want to display so I have to repeate code Im trying to find the best solution to not have to repeate same code sentences. TY in advance.

function loadJSON(callback) {
    var stringQuery = decodeURIComponent(window.location.search.replace(/^.*?\=/, ''));   
    var xobj = new XMLHttpRequest();
    xobj.open('GET', 'http://localhost:3000/data/?email='+stringQuery, true);
    xobj.onreadystatechange = function () {
      if (xobj.readyState == 4 && xobj.status == "200") {
      callback(JSON.parse(xobj.responseText));
      }
    };
    xobj.send(null);  
  };

function gettingReportbyEmail(){
    var stringQuery = decodeURIComponent(window.location.search.replace(/^.*?\=/, ''));
    var datos = {};
    var datos =  JSON.parse(localStorage.getItem(stringQuery));
    if (datos == null) {
      loadJSON(function(response){
      localStorage.setItem(stringQuery, JSON.stringify(response[0]));
      var datos = {};   //This is where I have to repeate same code as above
      var datos =  JSON.parse(localStorage.getItem(stringQuery));
      displayEmailandRelatives(datos);
      });  
    }else{
      datos = JSON.parse(localStorage.getItem(stringQuery)); 
    }
  };

no errors just trying to find a better solution.

Answer 1

 if (datos == null) {
      loadJSON(function(response){
      localStorage.setItem(stringQuery, JSON.stringify(response[0]));
      datos = response[0];
      displayEmailandRelatives(datos);
      });  
    }

I don't see any purpose of setting the value to localStorage and reading the same value just to call a function.

Answer 2

simply remove the duplicated code and it should work

function gettingReportbyEmail(){
    var stringQuery = decodeURIComponent(window.location.search.replace(/^.*?\=/, ''));
    // remove the code 
    if (datos == null) {
      loadJSON(function(response){
      localStorage.setItem(stringQuery, JSON.stringify(response[0]));
      displayEmailandRelatives(datos);
      });  
    }else{
      datos = JSON.parse(localStorage.getItem(stringQuery)); 
    }
  };

it should work because of JavaScript Closures https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures