CODEWITHSUNDEEP
javascriptjquery
Chrispy
Chrispy

Reputation: 331

Variable ends up undefined after using $.get

This seems like an incredibly simple issue but I have no idea why I'm getting undefined. I'm using jQuery to fetch data off a PHP script - specifically a string which the PHP file echoes. Here's the code:

<script type="text/javascript">

    var map1;

    $.get("script.php", function(data)
    {
        map1 = data;
    });

    alert(map1);

</script>

Now if I alert(map1), it ends up being undefined... why exactly is this the case? I thought by declaring map1 outside $.get, it would fix the problem but that's not the case. If I alert(map1) inside the $.get function, it ends up fine and the variable holds a string (as opposed to being undefined). So the question is... what's going on with map1? And how can I stop it from being undefined / going out of scope / whatever is happening to it?

Thanks in advance.

Upvotes: 1

Views: 155

Answers (5)

Barrie Reader
Barrie Reader

Reputation: 10713

What about doing it this way?

var map1;

$.ajax({ 
          type: "GET",
          url: "script.php",   
          async: true,
          success : function(data)
          {
               map1 = data;
               alert (data);
          }
});

Upvotes: 1

Neil Knight
Neil Knight

Reputation: 48537

As @Michael has put, the .get call is asynchronous so your javascript is executing this call, and then carrying on with your script, which is why you get an undefined alert box.

Your best option is to put in a success call:

$.get("script.php", function(data) 
{ 
    map1 = data; 
})
.success(function() { alert(map1); });

Upvotes: 3

osahyoun
osahyoun

Reputation: 5231

$.get runs asynchronously, and this is why the function's second parameter is an anonymous function. This anonymous function is invoked once $.get has finished executing. alert(map1) is invoked immediately, and not asynchronously. You could add the alert call to the anonymous function passed to $.get:

$.get("script.php", function(data){
  map1 = data;
  alert(map1);
});

Upvotes: 2

mas-designs
mas-designs

Reputation: 7536

Because your $.get fills the data slower than your alert is executed !
Which means your $.get function takes longer to compute than your alert !
You could use setTimeout() to work around this but I think its a bad practice.

Upvotes: 1

Michael Krelin - hacker
Michael Krelin - hacker

Reputation: 143051

Because your alert is executed before get finished. Put right after assignment in function body. get initiates the request and returns.

Upvotes: 4

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