Utilizing a modular perspective in JavaScript to load JSON files as a view

Question

Utilizing a modular perspective in JavaScript to load JSON files as a view

I've been working on implementing a modular view approach for retrieving data from a JSON file in my JavaScript code, but I'm facing some issues. The snippet of code where I am trying to load the JSON file is contained within a separate JS file and looks like this:

var fileConfigModule = (function () {

  var jsonData = {};

  function initialize() {
    loadJSON(function (json) {
      jsonData = json;
    });
    return jsonData;
  }

  function loadJSON(callback) {
    var request = new XMLHttpRequest();
    request.overrideMimeType("application/json");
    request.open('GET', './data.json', true);
    request.onreadystatechange = function () {
      if (request.readyState == 4 && request.status == "200") {
        callback(JSON.parse(request.responseText));
      }
    };
    request.send(null);
  }

  return {
    loadJSON: loadJSON,
    init: initialize
  }
})();

I want to utilize this module in my main file to asynchronously load the JSON data using a callback function. Here's how I plan to do it:

var jsonData = fileConfigModule.init();

If anyone can offer assistance on what might be going wrong here, I would greatly appreciate it. Thank you!

javascript json asynchronous modular

Answer 1

Answer №1

When you call an asynchronous function but expect a synchronous return value, it can lead to issues in your code.

To resolve this, consider updating your code as shown below:

var fileConfigModule = (function () {

  function initialize(callback) {
    fetchData(function (json) {
      callback(json);
    });
  }

  // The loadJSON function is actually hidden from view

  function fetchData(callback) {
    var xobj = new XMLHttpRequest();
    xobj.overrideMimeType("application/json");
    xobj.open('GET', './data.json', true);
    xobj.onreadystatechange = function () {
      if (xobj.readyState == 4 && xobj.status == "200") {
        callback(JSON.parse(xobj.responseText));
      }
    };
    xobj.send();
  }

  return {
    fetchData: fetchData,
    initialize: initialize
  }
})();

You should then call the function like this:

var arData = null;
fileConfigModule.initialize(function(data){
  arData = data;
});

If you're unsure why the loadJSON function is being hidden, consider using it directly instead of calling the initialize function.

By calling fetchData,

var arData = null;
fileConfigModule.fetchData(function(data){
  arData = data;
});

Answer 2

When you call an asynchronous function but expect a synchronous return value, it can lead to issues in your code.

To resolve this, consider updating your code as shown below:

var fileConfigModule = (function () {

  function initialize(callback) {
    fetchData(function (json) {
      callback(json);
    });
  }

  // The loadJSON function is actually hidden from view

  function fetchData(callback) {
    var xobj = new XMLHttpRequest();
    xobj.overrideMimeType("application/json");
    xobj.open('GET', './data.json', true);
    xobj.onreadystatechange = function () {
      if (xobj.readyState == 4 && xobj.status == "200") {
        callback(JSON.parse(xobj.responseText));
      }
    };
    xobj.send();
  }

  return {
    fetchData: fetchData,
    initialize: initialize
  }
})();

You should then call the function like this:

var arData = null;
fileConfigModule.initialize(function(data){
  arData = data;
});

If you're unsure why the loadJSON function is being hidden, consider using it directly instead of calling the initialize function.

By calling fetchData,

var arData = null;
fileConfigModule.fetchData(function(data){
  arData = data;
});

Utilizing a modular perspective in JavaScript to load JSON files as a view

Answer №1

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