insert array in other array in to a for loop,first result repeated

Question

I have a problem when inserting an array into another array in this loop:

function formToArray(frm){
    var sAux={};
    var AnnotationsQuestion={};
    var AllAnnotationsQuestion=[];

    for (i = 0; i < frm.length; i++) {

    //next line dont work
    sAux['question_id'] = frm[i].name.substring(13)
    sAux['answer']=frm[i].value;
    sAux['id']=0;
    AnnotationsQuestion['AnnotationsQuestion']=sAux;
    AllAnnotationsQuestion.push(AnnotationsQuestion);
    }

return AllAnnotationsQuestion 
}

this returns the first result repeated x times

example of a return value

[{'AnnotationsQuestion':{'question_id':4,'answer':
'AA'....}},{'AnnotationsQuestion':{'question_id':4,'answer':
'AA'....}}]

what is the problem of this loop?

You are not pushing a new object to AllAnnotationsQuestion on each iteration, rather a reference to the same object. Therefore, all elements of the returned array have the same value. If you do var sAux = {} at the beginning of your for loop, it should create a new object for that iteration, and then you will get unique values. — Rikonator
– Rikonator, Commented Jan 5, 2013 at 16:49
Yes, I also thought the same but putting Saux var = {}, at the beginning of each iteration, I got the same result — Martin
– Martin, Commented Jan 5, 2013 at 16:55
I do hope it was var sAux = {}; and not Saux var = {};... Anyway, look at the answer by @mplungjan, it's much cleaner. — Rikonator
– Rikonator, Commented Jan 5, 2013 at 16:58
I see. Yes, I'm sorry. The same object argument goes for AnnotationsQuestion as well. Once again, what you're pushing is a reference to a single object. Naturally, values are same across the board. You would have to do var AnnotationsQuestion = {}; at the beginning of each iteration, along with var sAux = {};. Check jsfiddle.net/rtSYC/3. — Rikonator
– Rikonator, Commented Jan 5, 2013 at 17:16

mplungjan · Accepted Answer · 2013-01-05 17:33:30Z

2

This is much safer and readable

DEMO

function formToArray(frm){
  var AllAnnotationsQuestion=[];

  for (var i = 0; i < frm.length; i++) {
    AllAnnotationsQuestion.push({
      'AnnotationsQuestion': {
        'question_id': frm[i].name.substring(13),
        'answer': frm[i].value, 
        'id':0 
      }
    });
  }
  return AllAnnotationsQuestion; 
}

edited Jan 5, 2013 at 17:33

answered Jan 5, 2013 at 16:53

mplungjan

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2 Comments

Martin Over a year ago

thanks for the answer, but I got this error with your solution 'Uncaught SyntaxError: Unexpected token : '

Martin Over a year ago

This error is the chrome browser, in this line 'AnnotationsQuestion': {

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