JavaScript global variables are experiencing issues with proper updates

I am facing an issue where I need lines to be stored in a global array. However, when I compare the values inside the function with those outside the function using console.log, I notice that the inside one works fine but the outside one remains empty. Can anyone guide me on what might be the problem here?

      var lines = new Array();
  $.ajax({
    type: "GET",
    url: "posts_replied_to.txt",
    success: function(content) {
      console.log("success");
      lines = content.split('\n');
      console.log(lines);
    },
    error: function() {
      console.log("error");
    }
  });
  console.log(lines);

Answer №1

The issue at hand does not revolve around global variables. Instead, it pertains to the problem of asynchronicity. The ajax success callback is not being called by the time the console.log() outside the ajax request is executed, causing the incorrect value to be displayed.

async function doAjax() {
    return await $.ajax({
        type: "GET",
        url: "posts_replied_to.txt"
    });
}

let lines = await doAjax()
lines = content.split('\n')
console.log(lines)

For the desired outcome, try utilizing Async in your code.

Answer №2

Indeed, AJAX operates asynchronously. This means that commands outside of the AJAX function, such as 'console.log(lines)', may run before the AJAX call is complete.

If needed, you can use the option 'asyn:false' in AJAX to make it synchronous.

Learn more about the effects of 'async: false' in jQuery.ajax() here.

Answer №3

Prior to receiving your GET response, your second console.log code will also run because the ajax call is not asynchronous. Make the following changes:

var entries = [];
 $.ajax({
   type: "GET",
   url: "posts_replied_to.txt",
   async: false,
   success: function(data) {
     console.log("Success!");
     entries = data.split('\n');
     console.log(entries);
   },
   error: function() {
     console.log("Error!");
   }
 });
 console.log(entries);

Answer №4

Consider utilizing the promise object that is returned by the ajax call.

var entries = new Array();
var promise_object = $.ajax({
    type: "GET",
    url: "retrieved_entries.txt"
}).promise();

promise_object.done(function(result) {
    entries = result.split('\n');
    console.log(entries);
    // Implement the remaining part of your code here using the entries.
});

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