JavaScript - Not able to assign to Variable in Loop

Question

I am trying to get Comments stored in the Firebase using the below example. The script is looping through the json object and appending the HTML results to a global variable. However, the assignment in the loop does not append to the global variable.

var doccmnthtml = '';

try {
    $.getJSON( "https://ocw.firebaseio.com/.json", function( json ) {
        for (var key in json) {
            if (json.hasOwnProperty(key)) {

// Cannot append to the variable
                doccmnthtml += '<b>'+json[key].username+'</b><br/>'+json[key].text+'<br/><br/>';
            }
        }
    });
}
catch(err) {
    console.log(err.message);
}

alert(doccmnthtml);

that's because `alert` outside the `try` hasn't been assigned any values yet when you call it, since the http request hasn't completed yet — Sylvan D Ash, Nov 10 '15 at 08:00

Kishore Sahasranaman · Answer 1 · 2015-11-10T08:01:48.683

2

The alert is outside the ajax call, as it is async the variable is not getting assigned.

See the below code : I have included the alert inside the success call.

var doccmnthtml = '';

try {
  $.getJSON("https://ocw.firebaseio.com/.json", function(json) {
    for (var key in json) {
      if (json.hasOwnProperty(key)) {

        // Cannot append to the variable
        doccmnthtml += '<b>' + json[key].username + '</b><br/>' + json[key].text + '<br/><br/>';
      }
    }
    alert(doccmnthtml);
  });

} catch (err) {
  console.log(err.message);
}

edited Nov 10 '15 at 08:01

answered Nov 10 '15 at 07:59

Kishore Sahasranaman

4,013
3
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1

Describe what you have changed. – Yeldar Kurmangaliyev Nov 10 '15 at 08:00
The issue is because the call is `async` and the `alert` is executing before the `success` function. I have update my answer. – Kishore Sahasranaman Nov 10 '15 at 08:03

score 0 · Answer 2 · answered Nov 10 '15 at 08:03

0

The problem is that getJSON is an a-sync call which means that your alert is called before the response is set.

You can fix this by calling an callback function in the success-response.

answered Nov 10 '15 at 08:03

Salmin Skenderovic

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JavaScript - Not able to assign to Variable in Loop

2 Answers2