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I have this in my HTML code

<script type="text/javascript">
    var URL = replace(); 
    alert(URL);
</script>

If I put this in header, alert shows “http://example.com/result"

function replace() { 
　url = 'http://example.com'; 
　$.get(url, function(data){ 
　　var url_gen = data.responseText; 
　}); 
　return “http://example.com/result"; 
}

But if I use return like this, it won't do anything. Why?

function replace() { 
　url = 'http://example.com'; 
　$.get(url, function(data){ 
　　var url_gen = data.responseText; 
　}); 
　return url_gen; 
}

Just to make sure, If I insert alert(url_gen) in front of return url_gen; in 2nd code, alert shows 'http://example.com' so url_gen has an actual value in it!

Note: Here, assuming that url_gen is the string which is web-scraped from a web page.

Peter O.
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HUSTEN
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2 Answers2

1

Because 1) url_gen only defined in $.get(), can't be accessed outside; 2) $.get() is async.

Workaround: return directly from $.get():

function replace() { 
　url = 'http://example.com'; 
　$.get(url, function(data){ 
　  var url_gen = data.responseText; 
    return url_gen;
　}); 
　 
}
Peter O.
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nicael
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  • Thanks now alert says "undefined" :( – HUSTEN Mar 29 '15 at 15:54
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    you receive undefined because you set alert on a response of ajax function. ajax has a delay to retrieve data but alert is triggered as soon as you call it. You have to make a sync ajax call (bad way because the window will freeze until your function is finished) or change your structure to set alert inside ajax response. – Ali Sheikhpour Mar 29 '15 at 16:25
1

Make url_gen global like below:

function replace() { 
url = 'http://example.com'; 
var url_gen ='';
$.get(url, function(data){ 
url_gen = data.responseText; 
}); 
return url_gen; 
}
Peter O.
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Samir Das
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  • Thanks for an answer. I tried your code, but now the alert says "undefined" instead of showing url – HUSTEN Mar 29 '15 at 16:00
  • It returns empty. as nicael said, $.get() is async so you should work or do necessary operation inside success callback. – Samir Das Mar 29 '15 at 16:20