Var is undefined

Question

Hi guys^ have such code:

<html>
<head>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6/jquery.min.js"></script>
</head>

<body>
<script type="text/javascript">
var array = [];
$.get("http://wisepla3nt.com/331.txt", 
       function(data) {
           array = data.split(/\r\n|\r|\n/)
       }
);
</script>
<script>alert(array[Math.floor(Math.random()*array.length)]);</script>
</body>
</html>

On alert have undefined. Why? array is global.

possible duplicate of [How to return the response from an AJAX call?](http://stackoverflow.com/questions/14220321/how-to-return-the-response-from-an-ajax-call) — adeneo, Sep 28 '13 at 11:13

score 5 · Accepted Answer · answered Sep 28 '13 at 11:01

The function you pass to get is not executed immediately. It is assigned as an event handler and fires when the browser gets a response to the HTTP request.

The response doesn't arrive until after the alert statement has fired.

Do the work that depends on the response in the callback function.

score 1 · Answer 2 · answered Sep 28 '13 at 11:02

1

Probably because you're alerting before your $.get function has returned.

The $.get method is an Ajax call which means it's asynchronous. Try moving your alert code into the callback method.

answered Sep 28 '13 at 11:02

royse41

2,310
4
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score 0 · Answer 3 · answered Sep 28 '13 at 11:03

0

get is asynchronous and you're calling alert right after it and before the response comes from a server

So the array is empty, array.length is zero and Math.random()*0 will return 0 but there's no array[0] so it returns undefined

answered Sep 28 '13 at 11:03

Adassko

5,201
20
37

score 0 · Answer 4 · answered Sep 28 '13 at 11:08

Move alert() right after array filling string.

<html>
<head>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6/jquery.min.js"></script>
</head>

<body>
<script type="text/javascript">
var array = [];
$.get("http://wiseplant.com/1.txt",
       function(data) {
           array = data.split(/\r\n|\r|\n/)
           alert(array[Math.floor(Math.random()*array.length)]);
       }
);
</script>
</body>
</html>

Var is undefined

4 Answers4