Index not taking the right value within an $http.post query

Question

I'm doing a loop like this :

for (var index in data) 
{
    console.log(index);    
    $http.post('server.php')
    .success(function(data, status) 
    { 
        console.log(index); 
    }
}

The first console.log() displays : 0,1,2,3,4,5

The second console.log() displays : 5,5,5,5,5,5

And I have really no idea why. Is it because of the fact that i'm using 2 variables named data ? I tried renaming one, but it didn't fixed the issue.

Possible duplicate of [JavaScript closure inside loops – simple practical example](http://stackoverflow.com/questions/750486/javascript-closure-inside-loops-simple-practical-example) — Nikhilesh K V, Apr 25 '16 at 12:47
@NikhileshKV Possibly, but the question must be a question, the link you proposed assumes the user knows what to look for. — SparK, Apr 25 '16 at 12:53

Rayon · Answer 1 · 2016-04-25T12:46:11.313

1

Use Closures, The function defined in the closure 'remembers' the environment in which it was created. [From docs]

for (var index in data) {
  (function(index) {
    $http.post('server.php')
      .success(function(data, status) {
        console.log(index);
      });
  })(index);
}

edited Apr 25 '16 at 12:46

answered Apr 25 '16 at 12:39

Rayon

36,219
4
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This one explains why you need closures. – SparK Apr 25 '16 at 12:44

Praveen Kumar Purushothaman · Accepted Answer · 2016-04-25T13:00:44.637

1

You need to use Closures in this aspect. The closure, "packs" the value of the index, while it gets executed at a callback, later.

for (var index in data) {
  (function(index) {
    $http.post('server.php')
    .success(function(data, status) {
      console.log(index);
    });
  })(index);
}

edited Apr 25 '16 at 13:00

answered Apr 25 '16 at 12:39

Praveen Kumar Purushothaman

164,888
24
203
252

score 0 · Answer 3 · answered Apr 25 '16 at 12:48

Closure. If it's hard to understand it's basically doing this:

function doPostCall(index) {
    $http.post('server.php')
    .success(function(data, status) { 
        console.log(index); 
    }
}

for (var index in data) {
    console.log(index);    
    doPostCall(index)
}

See, it's just separating the post into it's own function with it's own index variable that is guaranteed to not change from outside/

Index not taking the right value within an $http.post query

3 Answers3